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The Applicability of Weber's Law to 
 
 Smell 
 
 THESIS 
 
 PrBSBnted To van IlNirraRSiTY Facui<ty of Cornbi<i, University 
 
 FOR THE DEGREE OF 
 
 DOCTOR OF PHIIvOSOPHY 
 
 EI.EANOR ACHESON McCULLOCH GAMBLE 
 
 Reprint from the American Journai, of Psychox,ogy 
 Vol. X, No. I, October, 1898 
 
The original of this book is in 
 the Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924024829347 
 
THE APPLICABILITY OF 
 WEBER'S LAW TO SMELL. 
 
 Cornell University Library 
 QP 458.G19 1898 
 
 Applicability of Weber's law to smell. 
 
 3 1924 024 829 347 
 
 By 
 
 ELEANOR ACHESON McCULLOCH GAMBLE, A. B., Ph.D. 
 
 I<ate Fellow in Psychology at Cornell University, Instructor in 
 Psychology at Wellesley College. 
 
 REPRINT FROM THE 
 
 American Journai, of Psychology, Vol. X, No. i. 
 1898. 
 
THE APPLICABIUTY OF WEBER'S IvAW TO SMELL. 
 
 By El<EANOR ACHESON MCCULLOCH GAMBLE, Ph. D., 
 
 Cornell University. 
 
 CONTENTS. 
 Introduction. 
 
 Progress of the Experimental Proof of Weber's I/aw. 
 
 Object and Scope of this Paper. Its connection with Zwaardemaker's 
 
 Olfactometric Work. 
 Zwaardemaker's Terminology. 
 Defect of All Psychophysical Measurements. 
 The Peculiar Dif&culty of Olfactometry, viz., the Indeterminateness 
 
 of Olfactory Qualities. 
 Zwaardemaker's Classification of Olfactory Qualities. 
 Antecedent Probability of the Applicability of Weber's Law to Smell. 
 
 Chapter I. Method. 
 Section i. Factors which Determine the Intensity of the Smell- 
 Stimulus for the Normal Organ. 
 
 (I.) The Quantity of Vapor Thrown Off by the Odorous Body. 
 
 (II.) The Rate of Diffusion of the Odorous Vapor. 
 
 (III.) The Rate and Manner of Breathing. 
 
 Compensation of Smells. 
 
 Direct and Indirect Olfactometric Methods. 
 
 Methods of Valentin, Fischer and Penzoldt, Dibbits, Ottolenghi, 
 Passy, Frolich, Aronsohn, Savelieff. 
 Section 2. Control in Zwaardemaker's Olfactometric Method of the 
 Factors which Determine the Intensity of the Stimulus. 
 
 Treatment of the Two Factors of the Genetic Unit. 
 
 The Method of Henry. 
 
 Adhesion to the Inhaling-Tube. 
 
 Control of the Diffusion-Rate of the Vapor. 
 
 Control of the Manner and Rate of Breathing. 
 Section 3. Anosmia and Hyperosmia. 
 
 Method of Testing the Openness of the Nasal Passages. 
 
 The Effect of Exhaustion. 
 Section 4. Psychophysical Methods Employed. 
 
 An Imperfect Method of Finding the Stimulus-Limen. 
 
 The Method of Just Noticeable Differences. 
 
 Intervals between Stimuli and between Determinations. 
 
 The Method of Minimal Changes. 
 
 A Modified Form of the Method of Just Noticeable Differences. 
 
 The Subject's Tendency to Judge in Terms of Hand-Movement. 
 
 The Method of Right and Wrong Cases. 
 
 Chapter II. Apparatus and Materiai<s. 
 Section i. The Standard and the Fluid-Mantle Olfactometers. 
 
 (I.) The Standard Olfactometer. 
 
 (II.) The Fluid-Mantle Olfactometer. 
 Section 2. Preparation of Odorous Materials. 
 
WEBER'S LAW TO SMELL. 3 
 
 (I.) Preparation of Odorous Substances Used in Solid Form. 
 (II.) Preparation of Odorous Substances in Solution. 
 Section 3. Other Arrangements and Appliances. 
 
 Chapter III. Results. 
 Section r. The Several Subjects and their Stimulus-Limina. 
 
 Table I. A Table of Stimulus-Limina. Remarks. 
 Section 2. Results Obtained by the Method of Just Noticeable Dif- 
 ferences. 
 Table II. Consecutive Results for One Subject, T. Remarks upon 
 
 the Constant Sources of Error. 
 Table III. Complete Results for One Solid and One Liquid Sub- 
 stance. 
 Rough Summary of Results by Series. 
 
 Table IV. Approximate Values of A»^ Obtained for Pairs of Stan- 
 
 r 
 dard Stimulus-Intensities Sensed under the Same Conditions. 
 Curves Illustrating Parts of Table IV. 
 Lists of the Substances Used by the Several Subjects. 
 Table V. Approximate Values of Ar Arranged to Show Variations 
 
 for Individual Subjects. r 
 
 Table VI. Approximate Values of A^ Arranged to Show Variations 
 
 for Different Substances. ~ 
 
 Curves Illustrating Part 3 of Table VI. 
 Remarks on Tables V and VI. 
 Some Incidental Exhaustion-Phenomena. 
 Section 3. Results of Other Methods. 
 Table VII. Results of the Modified Form of the Method of Just 
 
 Noticeable Differences. 
 Table VIII. Results Obtained for Red Rubber by the True Method 
 
 of Minimal Changes. 
 Table IX. Results Obtained by the Method of Right and Wrong 
 
 Cases. 
 Table X. Results of a Rough Attempt to Gauge the Applicability 
 of the Method of Right and Wrong Cases to Smell. 
 Summary and Conclusion. 
 
 Introduction. 
 
 So long ago as 1834, in a paper entitled " De Tactu," Ernst 
 Heinrich Weber first stated the law which bears his name, the 
 first law of psychophysics. Working by the method afterwards 
 called by Fechner "the method of just noticeable difierences," 
 he had discovered the law in its application to pressure and 
 strain.^ Before i860 it had been proved to hold also for noise 
 and brightness. Since the establishment of the first psycho- 
 logical laboratory, which occurred in the academic year 1878-9, 
 and, oddly enough, but a few months after Weber's death, the 
 validity of the law for the four sensation qualities mentioned 
 has been over and over again confirmed. 
 
 Before i860 Volkmann, Renz, and Wolf, by the method of minimal 
 changes, had proved its applicability to noise. Bourger, Fechner, and 
 
 1 Wundt : Physiologische Psychologies 4th ed., I, p. 381. 
 
4 GAMBLE : 
 
 Volkmann, by their "shadow-experiments," and Masson with his ro- 
 tating disks, had shown, its validity for brightness. Fechner had also 
 established Weber's conclusions in regard to strain by the method of 
 right and wrong cases. In the last twenty years, Tischer, Merkel, 
 and Starke, by the method of minimal changes ; Merkel and Angell 
 by the method of mean gradations ; and Lorenz, Merkel, and Kampfe, 
 by the method of right and wrong cases, have confirmed for noise- 
 intensities the results of Volkmann ; Helmholtz, Aubert, and Krapelin 
 have established for brightness the results of Masson ; and Merkel, 
 using the method of minimal changes, has also proved the conclu- 
 sions of Weber and Fechner in regard to strain. In the last six 
 or seven years, the experiments of Merkel by the method of aver- 
 age error have proved the extension of the law to 'those strain- 
 sensations in terms of which we measure distance by the eye, and 
 the experiments of Schumann by the same method give some indica- 
 tion of its extension to strain-sensations involved in our estimate of 
 intervals between one-half second and three seconds. 
 
 In case of the sensation-modalities for which the law has not 
 been proved, and in the case of tone, there are great difficulties 
 in graduating the intensity of the stimulus. Articular sensa- 
 tions, indeed, are not themselves graduated intensively. In 
 the case of tone, the difficulty is mechanical, — that of grad- 
 uating minutely the objective intensity of simple periodic 
 vibrations. In the case of the two temperature qualities, which 
 are peculiar in depending on different intensities of a stimulus 
 from a physical point of view the same in kind, and in passing 
 into each other through a conscious indifference-point, the ex- 
 treme adaptability of the so far unknown and inaccessible periph- 
 eral organ makes the intensity of the physiological stimulus 
 begin to fall towards the indifference-point upon the applica- 
 tion of any new physical stimulus, and thus prevents the phys- 
 ical stimulus from being a measure of the physiological. The 
 sensation, moreover, varies in intensity with the extent of sur- 
 face stimulated and with the weight of the stimulating body. 
 
 The qualities of taste and smell form manifolds of indefinitely 
 related terms, which must be investigated separately. In the 
 case of taste, the list is at least closed. The intensity of the 
 taste sensation, however, is a function (i) of the degree of sat- 
 uration of the solution tasted ; (2) of the magnitude of the area 
 excited ; and (3) of the movement, diffusion, and pressure of 
 the substance tasted within the buccal cavity. , No very satis- 
 factory way of keeping all but one of these factors constant, 
 while that one is varied, has as yet been found, though the in- 
 vestigations of Camerer, who worked by the method of right 
 and wrong cases, make the law of Weber appear to apply to 
 salt and bitter. 
 
 As for the applicability of Weber's law to smell, the object of 
 this paper is to offer a mass of experimental difference-deterr 
 minations, with a statement of the ' ' checks ' ' or controls to 
 which they .must be subjected. This enumeration of possible 
 
WEBER S LAW TO SMELL. 5 
 
 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 i8o-i8r 
 and pages 188-194 in Die Physiologic 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 I^eipzig in 1895. The experiments to be de- 
 scribed 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 up- 
 ward to be inserted into the nostril. A shorter movable cylin- 
 der 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 far- 
 ther 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 ' ' olfac- 
 tometry " and "olfactometer" (replacing the older "osmom- 
 eter " ) , " odorimetry ' ' and ' ' odorimeter. ' ' Olfactometry is 
 that branch of psyx:hophysics which is concerned with the 
 measurement of the keenness of smell. ^ The distinction be- 
 tween 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 con- 
 cerned not with the sense-organ, but with the measurement of 
 the intensity of smell-stimuli considered as objectively as possi- 
 ble. ° 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 copipanion word ' ' ol- 
 facty."^ If, for example, a subject's stimulus-limen on the 
 olfactometer is 10 mm. when the normal stimulus-limen used is 
 
 ''■Die Physiologie des Geruchs, p. 78. 
 
 2 P. II. Cf. also Vintschgau, Die Physiologie des Geruchsinnes und 
 des Geschmacksinnes, in Hermann's Handbuch der Physiologie, III, 2, 
 p. 270. 
 
 ^Zwaardemaker: op. cit., p. 174. 
 
 *Pp. 92, 134-135- 
 
6 GAMBLE : 
 
 5 mm., then his stimulus-limen is two olfacties, and his olfactus 
 %. The olfacty used by olfactometry becomes for each sub- 
 stance the unit of odorimetry. Odorimetry is correlated with 
 photometry and phonometry. Both olfactometry and odorime- 
 try are branches of " olfactology " (to anglicise another word 
 used by Dr. Zwaardemaker). This again is correlated with 
 optics, acoustics and haptics. 
 
 The interdependence of olfactometry and odorimetry is not 
 unique. The unit of photometry, i. e. , the unit for the meas- 
 urement of light in the physical sense, is the illuminating 
 power for sensation of the light of some standard candle. "We 
 have no adequate objective method," writes Prof. Kiilpe, "of 
 ascertaining the intensity of the non-periodic and aperiodic 
 concussions which form the substrate of simple or complex 
 noises, independently of the statement of the observer whose 
 sensitivity we are testing. The phonometric determination of 
 sound intensities in psychophysical experiments is usually car- 
 ried out upon a principle similar to that employed in photom- 
 etry. As the objective stimulus- values in the apparatus em- 
 ployed, — say, elastic balls falling from a measurable height 
 on a resisting plate, — are determined by way of a subjective 
 comparison, the results are purely empirical, valid only for 
 the material used, the special circumstances of the observation, 
 etc."i 
 
 The peculiarly unsatisfactory character of the determina- 
 tions of olfactometry and odorimetry is due chiefly to the fact 
 that olfactory qualities, unlike visual and auditory, are not de- 
 marcated. It is true that it is more difficult to keep uniform 
 the duration and extension of smell-stimuli than it is to regu- 
 late these attributes for other stimuli, with the possible excep- 
 tions of temperature and taste. It is also true that the great 
 gulf of psychophysics, our ignorance of the physiological pro- 
 cesses which everywhere link the strictly physical to the psy- 
 chological, is wider in the cases of temperature, taste and 
 smell, than in the cases of vision, audition, pressure and strain. 
 Yet, at best, the measurements of physics must always be in 
 terms of sensation, and the measurement of sensation must 
 always be in terms of physics. 
 
 It seems wise to emphasize at the outset the initial difficulty 
 which makes all quantitative work in smell more or less un- 
 systematic, viz., the indeterminateness of olfactory qualities. 
 It is at present necessary to regard as a simple and separate 
 quality the odor of every substance which from a physical 
 point of view is unmixed ; yet, for several reasons, it is un- 
 
 ^ Outlines of Psychology, it., p. 156. 
 
WEBER'S LAW TO SMELL. 7 
 
 likely that there are as many elementarj. odors as there are 
 simple substances. ^ 
 
 One reason is, that it is extremely improbable that either the 
 structure of the fibres or endings, or the substance of the olfac- 
 tory nerve, is differentiated to correspond to the innumerable 
 odorous substances which we encounter; and, on the other 
 hand, it is probable by analogy with other sense-organs, that 
 there are ' ' specific energies ■' ' of smell which are limited in 
 number and capable of combination.^ 
 
 A second reason is that we have experimental evidence that 
 the action of the sense organ is differentiated into more and less 
 separable processes. We have sure evidence in the results of 
 exhaustion-experiments, which were first instituted by Frolich 
 and Aronsohn.' For example, a subject whose organ is 
 fatigued by the continuous smelling of tincture of iodine can 
 sense ethereal oils and ethers almost or quite as well as ever, 
 oils of lemon, turpentine and cloves but faintly, and common 
 alcohol not at all. We have also evidence of some slight value 
 in the recorded traces of partial anosmia.* Unfortunately, very 
 few such cases have been described by persons who took ex- 
 perimental precautions, and such cases as are noted in medical 
 literature fail to show typical anomalies comparable to the uni- 
 form phenomena of color-blindness or " tone- islands," which 
 have played such an important part in the formation of theories 
 of vision and audition.^ 
 
 A third reason is that there are countless instances of smell- 
 fusions in which the components cannot be detected. Nagel 
 intimates that there is no proof of the existence of smell- 
 fusions in which difierent components can be sensed as differ- 
 ent at the same instant, and points out that, in this respect, 
 smell-mixtures resemble color-mixtures rather than clangs.' 
 
 Zwaardemaker, following Aronsohn and bearing in mind the 
 usages of the perfume trade, holds that only similar odors will 
 
 ^It should be noted that the words "simple" and "mixed "or 
 " compound " are used here in the sense of physics proper, and not in 
 the sense of chemistry. Smell, in the physical sense, is undoubtedly 
 a property of the molecule, not of the atom. Indeed, most of the 
 elements are odorless. Sulphur and hydrogen, themselves odorless, 
 form sulphuretted hydrogen, one of the most offensive smelling gases 
 known. 
 
 2 Nagel : tiber Mischgeriiche und die Komponentgliederung des Ge- 
 ruchsinnes. Zeitschrift fur Psychologie und Physiologic derSinnesor- 
 gane, XV, pp. 82-83. 
 
 'Zwaardemaker: o^. «V., pp. 203, 204, 256-257. Aronsohn: Unter- 
 suchungen zur Physiologi des Geruchs. Archiv fur Physiologie, 1886, 
 pp. 342-346. 
 
 * Zwaardemaker : op. ctt., p. 259 sq. 
 
 5 Nagel: op. cit., p. 87. 
 
 ^Pp. 90-91. 
 
8 GAMBLE : 
 
 mix.^ He believes, on the basis of his own experiments, that 
 if dissimilar odors of different intensities are mixed, the weaker 
 odor will cancel part of the odor of the stronger, and will itself 
 be lost, and that if dissimilar odors of the same intensity are 
 mixed, both will disappear or will give but a feeble indetermi- 
 nate fusion." Zwaardemaker does not, as alleged by Nagel, 
 adduce his conclusions in regard to mixture as a buttress to 
 his localization and irradiation theory, though he does seek to 
 explain the facts of mixture and compensation, as he under- 
 stands them, in harmony with this theory/ Nagel, as opposed 
 to Zwaardemaker, believes, on the basis of his own experi- 
 ments, that any two smells will unite in a mixture which 
 for an instant, at least, will make a simple impression of 
 new quality.* He has never found an instance of complete 
 "compensation," but he agrees with Zwaardemaker that a 
 mixture of several smells is in general weaker than its indi- 
 vidual components, and that some combinations of strongly 
 odorous substances are almost odorless.* Nagel offers no ex- 
 planation of the phenomenon of compensation, nor does 
 Zwaardemaker explain it satisfactorily even on the basis of his 
 irradiation-theory. Perhaps it is safe to conclude that most 
 smells will mix. As Nagel suggests, there is no occasion in 
 the perfume trade to mix nauseating or hircine smells with 
 the odors of flowers, spices and resins. 
 
 A fourth and final reason for believing that there are not as 
 many simple odors as there are unmixed substances, is that 
 many simple substances have been found by experiment to have 
 composite odors. Chlorphenol and nitrobenzol are good ex- 
 amples of such substances.' 
 
 Now, if there are a limited number of specific energies of 
 smell, and if most smells are mixed, our ignorance of the ele- 
 mentary smells, and our consequent inability to isolate them, 
 have serious consequences for the value of olfactometric work. 
 This will be clearer if we consider the two methods which are 
 used to discover whether a smell is simple or composite. The 
 method of Passy consists in gradually increasing the dilution of 
 odorous substances, and depends upon the principle that since 
 the stimulus-limina of different odors are different, they must 
 disappear successively as the intensities of the different stimuli 
 are diminished equally.' However, it is at least possible that 
 
 '^Op. cit., p. 280. 
 
 ^ Pp. 167 and 284. 
 
 ' P. 279. 
 
 * Op. cit., 95. 
 
 5p, loi. 
 
 « Pp. 96-97. 
 
 'P. 96. 
 
WEBER 'S LAW TO SMELL. 9 
 
 odors which have very different stimulus-limina should have 
 the same difference-limina. The other method is that of ex- 
 haustion, and depends on the fact that different odors exhaust 
 the organ with different degrees of rapidity, so that a com- 
 pound odor, continuously smelled, will alter in quality as first 
 one and then another of its constituents disappears. One may 
 smell continuously the substance to be tested, or may smell it 
 before and after smelling repeatedly an odor very similar in 
 quality. The principle of the method is the same in both 
 cases. The permanency of the mixed odor depends primarily 
 on the equality of rate at which its different constituents 
 fatigue the organ. The more numerous the constituents, the 
 more permanent the quality of the mixture. This fact is well 
 recognized in the perfume industry. Fortunately for' the trade, 
 the odor of almost every flower (Sawer mentions jasmine as a 
 unique exception)^ may be simulated by compounding the 
 odors of other flowers. The odor of violet, for example, is 
 given by a blend of the odors of acacia, rose, Florentine iris, 
 tuberose and almond. The odors of most flowers, again, are 
 possessed by certain chemicals. To the mixture is usually added 
 some substance, such as styrax, amber, or vanilla, which 
 evaporates slowly, and smells strongly enough to compensate 
 parts of the other odors. This is done that quantities of the 
 other odorous substances large enough to allow for evaporation 
 may be put into the solution without raising the intensity of 
 the smell to the neighborhood of the terminal stimulus- 
 intensity.'' If, now, most smells are mixed, and if mixed 
 smells alter in quality as the organ becomes fatigued, and if 
 different olfactory qualities have not the same limina, then in 
 quantitative work in smell, we are seeking to determine values 
 which are continuallj' changing according to laws which we do 
 not know. 
 
 There is no classification of olfactory qualities, which is even 
 provisionally satisfactory from any point of view but a per- 
 fumer's. We give to odors the names of the objects which most 
 commonly give rise to them, or to something similar to them. We 
 speak of a " fishy smell ' ' as loosely as Homer, in the days when 
 the terminology of color was in its infancy, spoke of " thewine- 
 hued sea." Yet the name of an odor is clearly and indisputa- 
 bly applica;ble only to the smell of that object from which the 
 name is taken.' 
 
 Giessler's classification of odors may be of value to psy- 
 chology proper, but is of no value whatever to psychophysics. 
 
 1 Sawer : Odorographia, First Series, p. 94. 
 
 2 Zwaardemaker : op. cit., p. 285. 
 
 3 P. 208. 
 
lO GAMBLE : 
 
 The most satisfactory method of arriving at a classification ot 
 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 large group of odors, and utterly fail 
 for another group ; but on the contrary, is usually more or less 
 impaired for all odors. ^ Analysis by exhaustion is complicated 
 experimentally by the fact that smells do not fall away steadily, 
 but oscillate at the stimulus-limen, as do minimal sensations 
 in other departments. In the case of smell this oscillation de- 
 pends 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.^ 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 classi- 
 fication of Linnseus, 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 unsatis- 
 factory 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 :' 
 
 I. Ethereal smells — including all the fruit odors (a class 
 taken from lyorry). 
 
 II. Aromatic smells — including all such odors as that of 
 camphor, spicy smells, and the odors of anise and lavender, 
 lemon and rose, and almond. 
 
 III. Fragrant smells — including the odors of most flowers, 
 of vanilla, and of such gums as tolu and benzoin. 
 
 IV. Ambrosiac smells — including the odor of amber, and all 
 the musk odors. 
 
 V. Alliaceous smells — including the odors of garlic, asafoet- 
 ida, gum ammoniac, vulcanized India rubber, fish, bromine, 
 chlorine and iodine, etc. 
 
 VI. Empyreumatic smells — including the odors of toast, 
 tobacco smoke, pyridin, naphtha, etc., (a class taken from von 
 Haller). 
 
 VII. Hircine smells — including the odors of cheese, sweat, 
 rancid fat, etc., etc. 
 
 1 Op. cit., p. 86. ~ 
 
 2 P. 98. 
 
 8 Op. cit., pp. 233-235. 
 
WEBER'S LAW TO SMELL. II 
 
 VIII. Virulent smells — including such odors as that of 
 opium, ' ' Odor cimicis, ' ' etc. 
 
 IX. Nauseating smells — including the odors of decaying 
 animal matter, of faeces and the like. 
 
 The pungency of smells is not an olfactory quality, but is 
 due to the excitation of filaments of the trigeminus, which are 
 freely distributed in the Schneiderian membrane. The sensa- 
 tion is more like pressure than smell. When very strong it 
 becomes a tickling, and sneezing ensues. Persons who have 
 congenital or pathological defects of smell are said to have cul- 
 tivated these sensations by attention to such an extent that 
 they do duty for smells proper.^ Some smells which are not the 
 flavors of food sensed in expiration, seem to be tastes, as well 
 as smells. For example, we think of the odor of boiling syrup 
 as sweet, and say that curdled milk " smells " sour. This is 
 probably due to early 'association, which has indissolubly 
 fused certain taste-memories with certain smell-sensations ot 
 peripheral origin.^ It may, however, be due to the entrance 
 of sapid particles through the nose into the pharynx." Smells 
 are often blended with pressure sensations other than pungency 
 and with temperature sensations.* It is probable that there 
 is an element of pain in an impression of pungency, while 
 smells often give a "feeling of weight," pure and simple. 
 Whenever the subjects in these experiments spoke of the heat, 
 taste, pressure, pain, or pungency of an odor, their remarks 
 were carefully noted, on the supposition that such factors in the 
 total impression were disturbing in a quantitative investigation 
 of olfactory qualities proper. 
 
 Zwaardemaker's differentiation of the specific energies of 
 smell and localization of their actions on the olfactory mucous 
 membrane is not to our present purpose. We may simply 
 note in passing that he arranges the zones of their operation in 
 horizontal order, since the height to which the air current is 
 carried in the nose makes no difference in the quality of an 
 odor ; and that he rather ingeniously places the nauseating and 
 virulent smells farthest back and closest to the pharynx, in a 
 region where they may excite the reflexes of vomiting and 
 coughing by mere irradiation of nervous excitation without the 
 connecting link of central processes ; puts the hircine and am- 
 brosiac odors in the middle, on account of the connection of hy- 
 peraemia of the ' ' corpora cavernosa nasalia ' ' with the blood 
 supply of the generative organs ; and locates the fragrant, aro- 
 matic and ethereal smells farthest to the front, since the 
 
 1 Pp. 236-237. 
 2p. 211. 
 8 Pp. 211-212. 
 <P. 212. 
 
12 GAMBLE: 
 
 sneezing-reflex is most easily excited in the anterior portion of 
 the nasal cavities.^ Nagel's remark that Zwaardemaker's locali- 
 zation-theory leads to ' ' irresolvable contradiction ' ' is not quite 
 clear, but he is certainly right in saying that the theory has no 
 adequate basis. Aside from the lack of experimental evidence, 
 the arrangement of the several zones is too fancifully neat to 
 carry conviction with it; but Zwaardemaker himself empha- 
 sizes the fact that the essential part of his theory is simply the 
 arrangement of the operations of specific energies of smell cor- 
 responding more or less exactly to the classification of Lin- 
 naeus on the olfactory mucous membrane in the order of these 
 classes. " 
 
 Before bringing these introductory remarks to a close, it may 
 be noted that, aside from any experimental evidence which may 
 be offered, it is probable that Weber's law does apply to such 
 smells, mixed and unmixed, as we daily encounter. In the 
 first place we have the analogy of several other modalities of 
 sensation for believing that the law applies to simple olfactory 
 qualities. In the second place it has never been proved that 
 Weber's law applies merely to unmixed sensations. It has 
 been neither proved nor disproved for clangs, but many expe- 
 riences of ordinary life would lead us to believe that it does 
 apply to musical chords as wholes. Thus it may apply to 
 smell-fusions as wholes, and approximately correct difference- 
 determinations may be obtained for these wholes even while 
 their character is gradually altering. Since, in the present 
 state of our knowledge, no one can even pretend to be working 
 with simple olfactory qualities, all difference-determinations in 
 smell must proceed upon the assumption of this possibility. 
 Experimental results must be the only decisive evidence for or 
 against the theory, so that it is needless to discuss it farther in 
 this place. 
 
 In the third place the distinction drawn by Passy between 
 ' ' insistent ' ' and ' ' intensive ' ' smells, which is based upon a 
 classification of smells in the popular mind and confirmed by 
 other scientific men, is explained by the supposition that 
 Weber's law applies to smell with different values of Ar for diff- 
 
 r 
 erent qualities. In Zwaardemaker's language, and in the ordi- 
 nary language of this paper, the smaller the ' 'minimum percept- 
 ible " of a substance, the more intense its odor. Passy uses a 
 term, " pouvoir odorant," — which we may translate " insist- 
 ency," — for "intensity" in our sense. He says : "Tout lemonde 
 sent que le camphre, le citron, le benzine sont des odeurs for- 
 
 1 Pp. 262-265. 
 ^P. 265. 
 
WEBER'S I,AW TO SMELL. 13 
 
 tes, la vanille, I'iris des odeurs faibles," though vanilla has an 
 insistency one thousand times greater than that of comphor. 
 Besides this subjective basis of distinction between weak odors, 
 however insistent, and strong or intensive odors, he has five ob- 
 jective differentiae, (i) Weak smells have vague differences of 
 intensity. For example, vanilla and coumarine soon reach a 
 maximum of intensity which cannot be increased. Greater 
 concentrations simply become unpleasant. (2) Individual dif- 
 ferences are more evident for weak smells. (3) The daily 
 variations of sensitivity are more evident for weak smells. (4) 
 Exhaustion has more effect on weak smells. (5) Strong 
 smells hide the weak.^ In view of the first objective difference, 
 Zwaardemaker explains the subjective difference as follows : 
 As the strength of a sensation is estimated by the number of 
 grades of intensity by which it surpasses the liminal sensation, 
 and as the terminal stimulus is by definition that degree of in- 
 tensity beyond which increase cannot be shown for our human 
 sense organs with our mechanical appliances, it is obvious that 
 odors with large difference-limina must be subjectively weak, 
 and that subjectively weak odors must have large difference- 
 limina. Thus, the very rapid attainment by some smell- 
 stimuli of the terminal intensity would seem to indicate that 
 Weber's law applied to olfactory qualities, and that the differ- 
 ence-limen differed from quality to quality." 
 
 Unfortunately our own experimental results are at variance 
 with the second clause of the theory. They make Weber's law 
 appear to apply to smells as we find them, but show no great va- 
 riation of Ay from substance to substance. The difference-limina 
 
 r 
 even of camphor and vanilline seem much the same. If our fig- 
 ures are accepted as trustworthy, some other explanation than 
 the simple one of Zwaardemaker must be found for the distinction 
 of Passy. May it not be that, for phylogenetic reasons, ' ' intense' ' 
 smells have more affective value, more of what Miiller calls 
 " Eindringlichkeit,'" than have the smells which Passy calls 
 ' ' insistent ?' ' Or may it not be that the smells most useful to 
 human life exhaust the human sense-organ less after many in- 
 crements than smells less useful do after a few increments, 
 although the increments are relatively equal throughout ? The 
 need of some such explanation will be more or less clear as the 
 figures to be offered are more or less convincing. 
 
 ^Pp. 191-192. 
 
 *Pp. 192-193. 
 
 8 The " Eindringlichkeit " of a sensation depends in part upon its 
 intensity, and in part upon its affective value (G. E. Miiller, Zeitschr. 
 f. Psych, und Physiol, der Sinnesorgane, X, pp. 25-27). 
 
14 GAMBLE: 
 
 Chapter I. Method. 
 
 Section i. Determination of the intensity of the Smell-Stimulus 
 
 for the Normal Organ. 
 
 If all the nervous elements concerned in smell are in a nor- 
 mal condition, and if "compensation" does not come into play, 
 the intensity of an odor depends on the number of odorous par- 
 ticles in gaseous form which are acting on the olfactory nerve- 
 endings at the time. Perhaps it is safe to say that the intensity 
 is ordinarily a function of the number which are acting on the 
 rod-cells of the olfactory mucous membrane. ^ Whether or not 
 individual rod-cells are subject to cumulative stimulation, we 
 do not know, for we do not know even whether the stimulation 
 is chemical, thermal, or electrical,'' but we do know that the 
 intensity of the smell seems to depend on the extent of mem- 
 brane and therefore on the number of rod-cells stimulated, — 
 always supposing that the rod-cells are the olfactory cells proper. 
 
 Now the number of odorous particles which act at any given 
 time on the olfactory membrane of the normal nose depends, 
 first, on the quantity of vapor which the fragrant body is 
 throwing off; secondly, on the rate of the diffusion of this 
 vapor ; and thirdly, on the manner and rate of breathing. Let 
 us consider these facts separately. 
 
 I. The Quantity of Vapor Thrown off by the Odorous 
 Body. "Whether" says Zwaardemaker, "odorous particles 
 are set free by evaporation or chemical reaction, the mass of 
 odorous molecules which are given off from a solid body or the 
 surface of a liquid is, ceteris paribus, in compound proportion 
 to the time of exposure and extent of surface exposed.' 
 Zwaardemaker has invented a ' ' genetic unit ' ' for the measure- 
 ment of odor in the physical sense. It is the number of seconds 
 of exposure multiplied by the number of square millimeters of 
 surface exposed.^ It is unnecessary to say that the genetic 
 unit differs from substance to substance. The ' ' other factors ' ' 
 which must remain equal, if the genetic unit of a given sub- 
 stance is to be constant, are the moisture, weight, and temper- 
 ature of the atmosphere and the amount of ozone present in it.° 
 
 That heat and dampness affect the intensity of odors is a 
 matter of common observation. Yellow wax smells twice as 
 strong in summer as in winter. Heat promotes evaporation. 
 Dampness also promotes the vaporization of such solids as are 
 
 1 Zwaardemaker : 
 
 op. cit., p. 7 ; Foster: 
 
 Text Book of Physiology, 
 
 6th ed., p. 249. 
 
 
 
 2 Zwaardemaker ; 
 
 op. cii., pp. 276-277. 
 
 
 8 P. 39. 
 
 
 
 <P.26. 
 
 
 
 6 P. 28. 
 
 
 
WEBER'S LAW TO SMELL. 15 
 
 soluble in water, but, on the other hand, retards the diffusion 
 of odorous vapors. The temperature of the laboratory in 
 which smell experiments are in progress should be kept as uni- 
 form as possible, and thermometer and barometer readings 
 should be taken whenever the stimulus-limen is determined. 
 Uniformity of temperature was not secured in our own experi- 
 ments. 
 
 II. The Rate of Diffusion of Odorous Vapor. Cloquet 
 pointed out in 1821 that odors diffuse in the air as one gas 
 diffuses in another, — gradually, and without interruption by 
 reflection or refraction, — so that if the air is at rest, the 
 strength of a smell will be inversely proportional to the distance 
 of its source, though the speed with which different odors 
 travel varies much.^ Now the air from which we draw our 
 breath is, under ordinary circumstances, almost never free 
 from currents. For phylogenetic reasons, no gas is odorous 
 which is not heavy enough to remain near its source if undis- 
 turbed. Yet the wind may carry such gases for miles near the 
 surface of the ground. Nor can we, in view of the dynamic 
 theory of smell, and of lyiegois's theory that odorous particles 
 are largely diffused in the form of tiny liquid drops which 
 afterwards vaporize, unhesitatingly apply the laws of diffusion 
 of gases to smells. Zwaardemaker has, however, proved by a 
 series of experiments that the transmission of odorous vapors 
 in tubes takes place at the same rate for different distances 
 from the source, unless these distances are very considerable.'' 
 From an inhaling-tube, all currents of air, except , the suction- 
 current created by the inspiration, are excluded. 
 
 III. The Rate and Manner of Breathing. Not all the air 
 which passes through the ncjse comes in contact with the olfac- 
 tory mucuous membrane. The current of air drawn into the 
 nose from without is divided by the lower turbinal bone into 
 two portions. From the stream which takes the direct path to 
 the choana under this bone and along the floor of the nose, no 
 odorous vapor reaches the olfactory membrane. Each nasal 
 cavity is divided by the middle turbinal bone into two cham- 
 bers. In the upper chamber, which extends from the pointed 
 roof of the nose to the under edge of the middle turbinal bone, 
 the side wall and the septum are almost parallel, and only 
 about two millimeters apart. The olfactory membrane is 
 spread over the upper surface of these parallel walls, forming 
 the regio olfactoria of Todd and Bowman. According to von 
 Brunn only the uppermost part of the upper turbinal bone and 
 the surface of the septum just opposite are covered by the ol- 
 
 iP.30. 
 
 2 Pp.31-34,39-40. 
 
1 6 GAMBLE : 
 
 factory membrane.^ In ordinary breathing, the highest point 
 in the upper stream is, according to Franke, the under edge of 
 the upper turbinal bone, and according to Paulsen and Zwaar- 
 demaker, the under edge of the middle turbinal bone." In the 
 rapid and violent breathing with expanded nostrils which we 
 call " sniffing," the air is carried about 2 mm. higher,' — i. e., 
 into the forward and under part of the upper chamber. In 
 either case, odorous particles can reach the olfactory membrane 
 only by diffusion, but more of them will penetrate to it in 
 sniffing than in quiet inspiration. The upper chamber is an 
 annex, not an integral part, of the breathing-passage. 
 
 Odorous particles probably do not accumulate in the upper 
 chamber. During inspiration, the air in the passages traversed 
 by the current is thinned, and as soon as inspiration ceases, the 
 air in the upper chamber rushes down to the middle meatus, to 
 be renewed from the pharynx during expiration.^ If so much 
 odorous matter has been taken in as to saturate the air in the 
 pharynx, we sometimes get a smell in expiration even when 
 we are not eating. Ordinarily, however, the very weak stimu- 
 lus from the pharynx, coming after the very strong stimulus 
 from without, is not sensed.^ Fick, indeed, advanced the hy- 
 pothesis that when odorous particles come in contact with the 
 olfactory membrane, they are at once dissolved in the thin fluid 
 which covers the bottom of the sensitive hairs, and that when 
 so dissolved, they cease to act.' These particles may, how- 
 ever, accumulate to some extent on the Schneiderian mem- 
 brane, especially, if it is in a catarrhal condition. Of course, 
 we get the flavor of food only in expiration. The course of 
 the air in expiration is almost the same, as in inspiration, but 
 Bidder is probably right in supposing that a smaller amount 
 passes above the lower turbinal bone.' 
 
 Under ordinary conditions, the more rapid the breathing, the 
 more intense the smell. Sniffing is to be forbidden in olfacto- 
 metric work, not merely because it carries the air higher in the 
 nose, than does ' ' regular breathing, ' ' but because, both by in- 
 creasing the suction-force and by widening the entrance, it 
 takes more air and therefore more odorous particles into the 
 nose in a given time. The spaces from which air is drawn 
 through the nose are cones with their points at the nostrils. 
 We may see their size and shape in the clouds of vapor formed 
 
 ip. 6. 
 
 2 Pp. 46-57. 67- 
 8 p. 202. 
 4 P. 60. 
 6 p. 62. 
 
 6 P. 60. 
 'P. 42. 
 
WEBER'S LAW TO SMELL. 17 
 
 by our exhalations in cold weather. The spaces from which 
 odorous particles are drawn are portions of these larger spaces. 
 The breathing-spaces are projections of the whole of the nasal 
 cavities; the "fields of smell" are projections only of those 
 cavities from which odorous particles reach the olfactory mem- 
 brane. They are separated from each other by about a centi- 
 meter. In sniffing, through the expansion of the nostrils, the 
 fields of smell become wider than the ordinary breathing-spaces, 
 but as the inspiration is short and quick, they are not so deep.^ 
 
 If then the strength of a smell-stimulus is to be measured 
 with some degree of accuracy by the genetic unit, the tempera- 
 ture and moisture of the air, the diffusion-rate of the vapor, 
 and the subject's manner and rate of breathing must be kept 
 as uniform as possible. 
 
 As for the compensation-error, there is no intrinsic stimula- 
 tion of the olfactory membrane as there is of the retina and the 
 ear. Owing to exhaustion, the subject cannot smell his own 
 breath in expiration. He can indeed smell it in inspiration if the 
 current is puffed upward to the nostrils. This fact seems to 
 show that, given the same amount of odorous matter in the air 
 current, we get a stronger smell in inspiration than in expira- 
 tion. On the other hand, the difficulty of securing an absence 
 of smells from external sources for a subject who has at all 
 cultivated his organ by attention, transcends the difficulty of 
 securing such silences and darknesses as are satisfactory for 
 experimental purposes. Of course, no substance which, as suck, 
 is to be used as a test, should be dissolved in an odorous 
 medium, such as alcohol, ammonia, or ether. 
 
 Zwaardemaker classes the methods which have so far been 
 employed to find the stimulus-limina of smells as direct and 
 indirect.'' By the direct methods the subject seeks to find the 
 stimulus-limen of an olfactory quality in terms of the greatest 
 dilution of an odorous vapor which can give a just noticeable 
 sensation of that quality. By the indirect methods, he seeks 
 to find the stimulus-limen in terms of the smallest quantity of 
 the odorous substance which can be sensed under certain defi- 
 nite and easily procurable conditions. The direct methods aim 
 at absolute results where absolute results are unattainable. 
 "It may be possible," says Zwaardemaker, " to determine the 
 area of an inspiration made in an effort to smell, but the exact 
 ascertainment of the amount of odorous gas which in this in- 
 spiration comes in contact with the olfactory cells has so far 
 proved an impossibility."^ The indirect methods aim at rela- 
 tive results, but their procedure is exact. They furnish a 
 
 1 Pp. 68-77. 
 
 2 Pp. 79-80. 
 8 p. 80. 
 
1 8 GAMBLE : 
 
 basis for the comparison of individuals with reference to their 
 keenness of smell, and of substances with reference to their 
 value for the sense, and thus may indirectly lead to some 
 knowledge of the greatest degree of dilution in which an odor- 
 ous substance can be detected.^ 
 
 The method which Valentin invented in 1848 maybe called classi- 
 cal, since it is mentioned in most of the standard text books of 
 physiology. It was direct, and consisted in taking a certain volume 
 of odorous gas and mingling it with a hundred volumes of air, taking 
 a certain volume of the mixture and mingling this again with a hun- 
 dred volumes of fresh air, and so on until the last mixture gave a just 
 discernable odor. Valentin varied his procedure by allowing the 
 vaporization of smaller and smaller quantities of a highly concen- 
 trated solution of an odorous substance in a definite amount of air, or 
 by mingling smaller and smaller quantities of it with a mass of 
 water of a given volume.^ It is plain that a certain amount of the 
 odorous substance must adhere to the vessel in which such a mixture 
 is contained, so that the amount of odorous substance taken away 
 from the receptacle for a new admixture will never be so large as the 
 ratio of the gas or liquid removed to the whole volume would indi- 
 cate, and that this error must increase as the experiment proceeds. 
 As for the use of highly concentrated solutions, it involves two 
 serious disadvantages, the blunting of the sense by exhaustion and 
 the adhesion of odorous particles to objects in the laboratory.^ 
 
 The invention of no other direct olfactrometric method is recorded 
 before that of the method employed by Fischer and Penzoldt in 1887. 
 Avoiding Valentin's progressive dilutions, these investigators sought 
 to determine how much mercaptan and how much chlorphenol must 
 be introduced into the whole mass of air in a laboratory of a certain 
 size in order to give an odor just noticeable to a person entering the 
 room. The walls of the laboratory were perfectly smooth, the floor 
 was of stone, and the equal distribution of the odorous gas to all parts 
 of the room was secured by the motion of fans. The solutions were 
 scattered with a fine spray.* Unfortunately, these solutions were 
 alcoholic. 
 
 In the same year H. C. Dibbits arrived at a partial determination of 
 the stimulus-limen for the odor of acetic acid. Acetate of zinc 
 is decomposed in the presence of water, and an insoluble basic salt 
 and free acetic acid are formed. Dibbits, during the course of six- 
 teen hours, allowed 60 litres of damp air to pass over a mass of salt 
 which had been freed from water of crystallization, found the loss of 
 weight to be 16.8 mg., and calculated the proportion that the weight 
 of the acetic acid set free must bear to this loss of weight to be ^. 
 As 24 mg. of acetic acid must have been communicated to 60 1. of air, 
 and as the odor was discernible in this air, the stimulus-limen of 
 acetic acid must lie under 0.4 mg. per litre.^ While the methods of 
 Fischer and Penzoldt and of Dibbits are comparatively accurate, it is 
 obvious that they are impracticable for difference-determinations. 
 
 A method employed in 1889 by Ottolenghi for testing the olfactory 
 sensitivity of criminals is a modified form of Valentin's, and is essen- 
 tially the same as the method recommended by Passy in 1892. 
 
 1 P. So. 
 
 2 Valentin: Grundriss der Shysiologie, p. 515. 
 
 'Zwaardemaker: op. cit., p. 79. 
 
 ^ American Journal 0/ Psychology, I, p. 357. 
 
 ^ Zwaardemaker : op. cit., p. 84. 
 
WEBER'S LAW TO SMELL. I9 
 
 Ottolenghi used 12 aqueous solutions of essence of cloves contained 
 in similar bottles in similar quantities. The solutions were graduated 
 from 1:50000 to 1:100. The subject began with the weakest solution 
 and took the bottles successively until sensation commenced. Passy 
 dissolved a certain weight of odorous material in a given weight of 
 alcohol, mingled a certain fraction of th* solution with a given weight 
 of pure alcohol, and so on, until he had obtained a graduated series of 
 saturations. He then put single drops of his solutions into bottles of 
 the same size, and arrived by the method of just noticeable stimuli at an 
 estimate of the stimulus-limen in terms of saturation-strength and the 
 area of his bottles. ^ Ottolenghi' s combinations of essence of cloves 
 and water were not true solutions. Passy's results are vitiated by the 
 compensating effect of the odor of the alcohol. Both methods involve 
 an error due to the constant loss of odorous material by the mere 
 opening of the vessels for the subject to smell their contents, by in- 
 halation, and by condensation on the walls of the vessels. Zwaarde- 
 maker suggests that fairly satisfactory results might be obtained on 
 Ottolongh i's principle if one (l) employed only solutions in distilled 
 water, (2) made very short inspirations, (3) used very large inhaling 
 vessels, and ( 4) avoided all odorous substances the vapor of which 
 is easily condensed.^ Theoretically, if the series of saturations could 
 be minutely enough graduated, this method might be employed for 
 difference-determinations, but practically, the use of many large in- 
 haling-vessels would make it too clumsy. 
 
 The first indirect method was invented by Frolich in 1851, three 
 years after Valentin invented his direct method. Frolich gauged the 
 keenness of smell by the distances at which odorous substances could 
 be sensed under uniform conditions. He put up in tightly corked 
 test-tubes such substances as ethereal oils, resins, spices, and musk 
 mixed with starch in such proportions that however different in 
 quality, the odors might be the same in intensity. The subject closed 
 his eyes, the tube was uncorked and moved toward him, and both 
 the distance at which the substance was first sensed and the time at 
 which judgment was passed were marked.' Frolich seems, however, 
 to have made little use of his time-estimates. As the odors with 
 which he worked are slowly diffused, the mass of odorous vapor may 
 be thought of as moving with the tube. Yet results based on such a 
 rough hypothesis cannot be very reliable.* Moreover, the assump- 
 tion that odors so unlike in quality are of the same intensity, since 
 they can be just sensed by the same person at the same distance, begs 
 the question of the value of the hypothesis mentioned, and Frolich 
 seems to have had no other means of determining their comparative 
 intensity except guess-work. 
 
 Aronsohn's famous method, devised in 1886, though indirect upon 
 the ordinary theory of smell which makes the odorous particles act 
 in gaseous form on the olfactory membrane, must be classed on Aron- 
 sohn's own premises as direct. His hypothesis is that odorous parti- 
 cles are in solution when they act on the nerve-endings. This 
 assumption, for which J. Miiller is chiefly responsible,^ is based (i) 
 on the fact that fishes and amphibia have peripheral and central or- 
 gans similar to the organs of smell in birds and mammals, and (2) on 
 the fact that the nasal membranes are normally covered with mucus, 
 
 iPp. 98-99. 
 = P. 99. 
 spp. 80-81. 
 
 4P. 81. 
 
 'P. 62. 
 
20 GAMBLE : 
 
 and that the drying of this mucus, as in the first stage of rhinitis, 
 impairs the sense of smell. Tortual and Weber had indeed proved 
 that odorous liquids when introduced into the nose " do not smell," 
 and Weber had also found that the sense is for a time impaired if 
 warm or cold water or sugar and water are poured into the nasal cavi- 
 ties and retained there for a few moments.* Aronsohn explained these 
 phenomena by supposing that strong solutions of odorous matter and 
 liquids of foreign temperature if brought in contact with the delicate 
 olfactory membrane must necessarily have a pernicious effect. He 
 found, on the other hand, that very small quantities of odorous sub- 
 stances dissolved in normal saline solutions can be sensed if the 
 mixture, at a temperature of about 40° C, is poured into the nose from 
 the height of about half a meter. Weber had used cologne and water 
 in the proportion of i : 11. Aronsohn used oil of cloves, for example, 
 in salt and water in the proportion of i : 500. His olfactometric 
 method consisted simply in determining how weak a solution of an 
 odorous substance could be sensed if injected at the temperature 
 proved empirically to be most favorable for its detection." If Aron- 
 sohu's premises are correct, not only is his method direct, but the 
 worst difficulties in the measurement of smell-stimuli are eliminated. 
 In criticism of these premises, however, Zwaardemaker points out (i) 
 that aquatic mammals have organs which resemble the organs of 
 smell in land mammals, but are rudimentary, as if useless under 
 water ; (2) that the dryness of rhinitis is confined almost exclusively 
 to the Schneiderian membrane and is conjoined with hyperaemia and 
 swelling which obstructs the passage of air; (3) that the cilia of the 
 olfactory cells protrude through the covering of mucus ; and (4) 
 that most odorous substances are not at all or are but 'very slightly 
 soluble in water. Books on the perfume-industry are filled with the 
 discussion of ethereal oils, of spices, gums, and the like. In a room 
 saturated with perfume or tobacco smoke, a bit of cotton wool will 
 take up the odor, while a glass of water will not. Moreover, as 
 Zwaardemaker believes, it cannot be shown that Aronsohn succeeded 
 in filling the cavity which contains the olfactory membrane so en- 
 tirely with liquid that all bubbles of air were excluded. It is very 
 difficult to drive all the air out of blind pouches.^ 
 
 In 1893, Dr. N. Savelieff in the laboratory of Morokschowetz con- 
 structed an olfactometer on a principle entirely different from Zwaar- 
 demaker's. There were two flasks of glass, each with two corks. 
 Through one cork in each, the two flasks were connected by a glass 
 tube bent twice at right angles. Through the other cork of one was 
 inserted a glass tube which reached to the bottom. Through this tube 
 a mixture of ethereal oil and water was poured. The liquid did not 
 reach the end of the connecting tube. Through the remaining cork 
 of the second flask, which was filled only with air, was inserted a 
 glass inhaling-tube which divided into a nose-piece for each nostril. 
 The odor of the liquid was weakened by successive additions of water, 
 and the intensity of the stimulus was measured through the propor- 
 tion by weight which the ethereal oil bears to the water.* As Zwaar- 
 demaker suggests the method of Savelieff has this great disadvant- 
 age, that its results do not stand in simple relations to the real stim- 
 ulus-intensities. The intensity of the stimulus will vary according 
 to the height of the liquid in the first vessel, and according to the ad- 
 
 1 Weber: Archiv f. Physiologie, 1847, p. 351-354. 
 
 ^Aronsohn : op. cit., 1886, pp. 324-332. 
 
 ^ Op. cit., pp. 62-66. 
 
 * Neurologtsches Centralblatt, 1893, p. 343 sq.* 
 
WEBER'S LAW TO SMELL. 21 
 
 hesion of odorous material in different parts of the apparatus. Sav- 
 elieff's method would indeed be fairly satisfactory for clinical pur- 
 poses if real solutions were used instead of mixtures of ethereal oils 
 and water. It is a great disadvantage, however, to begin an experi- 
 ment by exhausting the sense-organ with a saturated solution.^ 
 
 Section 2. Control hi Zwaardemaker' s Olfactometric Method of 
 the Factors which Determhie the Intensity of the Stimulus. 
 
 Zwaardemaker' s measurements ol the smell-stimulus are in 
 terms of but one factor of the genetic unit, — viz. , in terms of 
 the amount of odorous surface exposed. The time for which 
 different extents of surface are exposed is supposed to be kept 
 constant by the regularity of the movement of the hand which 
 manipulates the odorous cy4inder. All of these time-values 
 are so small that their variation may well be disregarded. 
 
 In 1890, Henry, a French scientist, instituted in the interests of the 
 perfume industry a modified form of Zwaardemaker's method, and 
 took the time values into account. His instrument differs from 
 Zwaardemaker's only in the substitution for the odorous cylinder of a 
 porous paper cylinder, hollow, closed at the bottom, and saturated 
 from a surrounding glass reservoir with the fumes of an odorous 
 liquid. The glass inhaling-tube enters from the top, and the subject 
 raises it with a uniform movement while he is making the inspiration 
 required. Stimulus-intensity is reckoned in terms of the surface of 
 the paper cylinder exposed, and of the time which the odorous vapor 
 has had for diffusing into it since the lifting of the inhaling tube.'' 
 As for this second factor, by which alone Henry's method differs from 
 Zwaardemaker's, Passy suggests that the time-rate of evaporation of 
 a liquid under a membrane differs from the time-rate of the same fluid 
 in the open air. Henry supposes that the pressure of vapor on the 
 paper cylinder is constant, but on the contrary, since its surface is 
 wholly covered at the beginning of the experiment and is gradually 
 uncovered as the glass tube is raised, the pressure of vapor will con- 
 stantly decrease.' At any rate, Henry's apparatus will not answer for 
 difference-determinations, as it would render procedure in both direc- 
 tions impossible. 
 
 Much more serious in Zwaardemaker's method than any 
 error which may arise from irregularity in the subject's move- 
 ments is the error due to the adhesion of odorous particles in 
 the glass inhaling-tube. These particles may condense on the 
 sides of the tube or, if the substance is soluble in water, may 
 dissolve in the moisture which forms on the inside during in- 
 spiration. A correction can be made for adhesion only for the 
 ' ' minimum perceptible, ' ' and only for a determination taken 
 with the perfectly dry and clean inhaling-tube and a saturated 
 porcelain cylinder. It may be made as follows : I,et the 
 length of the inhaling-tube ordinarily used be x and let a be 
 the value of the stimulus-limen as found with it. Then let a 
 
 * up. cti., pp. lOO-lUl. 
 
 ^Comptes rendus de V Academic des Sciences, Feb. 9, 1891. 
 s Zwaardemaker : op. cit., p. 94. 
 
22 GAMBLE : 
 
 shorter inhaling-tube of the same diameter and the length y be 
 pushed for about 2 mm. into the odorous cylinder. Through 
 the other end of this cylinder, which is usually the movable 
 part of the instrument, let a third tube of the same diameter be 
 pushed. By moving this third tube backward and forward, 
 the extent of odorous surface exposed to the air is varied. Let 
 the stimulus-limen found under these conditions be b. Then 
 a - b will be the difference in the stimulus-limen made by the 
 adhesion of odorous particles to a tube of the length x — -y. 
 The correction to be made for adhesion to a tube of the length 
 X will be as much greater as x is greater than x — y. If cylin- 
 ders of solid odorous substances be used, this correction cannot 
 be made, even for the stimulus-limen, since it is so exceedingly 
 small. It is impossible, moreover, to take many determin- 
 ations even of the stimulus-limen in an hour with a perfectly 
 dry and clean tube. As for the difference-limen, it is both 
 theoretically and practically impossible to make the adhesion- 
 correction, for to know how much greater for sensation a 
 given stimulus is than the liminal stimulus, one would have 
 to know beforehand that Weber's law applied to that particular 
 olfactory quality, and what the exact value of Ar for the quality 
 
 r 
 was. The effect of adhesion, in the first inspiration or at 
 least in the very first few inspirations, is to decrease the 
 strength of the stimulus, but after the first or at most after the 
 second or third inspiration, the efiect is rather to increase 
 the strength of the stimulus, since the odor from the matter 
 adhering to the inhaling-tube more than compensates for the 
 loss of the odor of the matter which continues to adhere. . 
 
 The tube must be carefully dried after it has been washed, 
 and the subject must be trained not to breathe back into it. 
 Yet on a damp day, the moisture left on the inside of the tube 
 by the inspired air is no inconsiderable source of error. Bun- 
 sen computes the possible thickness of such a layer at o.ooioi 
 mm. If a glass tube is 15 cm. long and 5 mm. wide, the area 
 of its bore will be 23.57 qmm. This would make the weight 
 of a layer of moisture of the thickness given by Bunsen 2.38 
 mg. If the odorous substance is in aqueous solution, this 
 moisture may be left out of account, but if no moisture comes 
 from the cylinder itself, it may vitiate the results of the experi- 
 ment. Since the dampness of the air varies from day to day, 
 this error cannot well be corrected.^ All that one can do is 
 faithfully to take the barometer-readings in the hope of finding 
 in them possible explanations of erratic judgments. The ex- 
 perimenter must be careful to cool the inhaling-tube after dry- 
 
 >Pp. 124-125. 
 
wbber's law to smkll. 23 
 
 ing it over the spirit-flame, not only on account of the risk of 
 distracting the subject's attention with a warm tube, but on 
 account of the danger of heating the inside of the odorous 
 cylinder. 
 
 Since the source of the odorqus vapor is connected with the 
 subject's nose by a tube of known length, the diffusion of the 
 matter is, outside of the body, obviously under complete control. 
 
 Thesubject'sbreathingis, indeed, a seriously variable element, 
 but its variation is by no means the greatest practical draw- 
 back to the method. Sniffing must, of course, be watched for 
 and peremptorily forbidden. The mere expansion of the nos- 
 trils does not increase the intensity of the odor as it does under 
 ordinary circumstances, but rather decreases it, since the field 
 of smell is artificially limited, and the widening of the en- 
 trance to the nose simply increases the amount of air which 
 dilutes the odorous gas. Under ordinary circumstances, as we 
 have seen, the more rapidly one breathes, the stronger the 
 odor one will get. If one uses the olfactometer, this is not 
 true. Since the diffusion-rate within the cylinder is constant, 
 increased rapidity of breathing will increase the degree in 
 which the odorous particles are diluted with air on their en- 
 trance to the nasal passages. Thus, the more slowly one 
 breathes, within a certain limit, the stronger the smell one will 
 get. The air must be drawn in with enough force to carry part 
 of the current above the lower turbinal bone. If the air simply 
 takes the straight path to the choana along the floor of the 
 nasal cavity under the lower turbinal bone, there will be no 
 smell. Zwaardemaker believes that each subject with a little 
 practice will discover for himself the best rate of breathing for 
 obtaining the strongest smell from a given stimulus, so that, in 
 a manner, the breathing rate will be self-regulating.^ Our 
 own experimental results seem to bear out this conclusion. In 
 Section i of Chapter III, each subject's mode of breathing is 
 noted, but its peculiarities can scarcely be traced in the 
 numerical results. The inability of most of the subjects to 
 arrive at difference-determinations with one inspiration must, of 
 course, have aggravated the adhesion-error. Henry regulates 
 the breathing of his subjects bj' putting about the chest a belt 
 which allows only a certain expansion. Such an appliance 
 must, however, have the effect of distracting the subject's at- 
 tention and making the breathing unnatural. Following 
 Zwaardemaker' s example, we did not even stop the nostril not 
 in use. The inhaling-tube was thrust into the forward" half 
 of the nostril to the depth of half a centimetre. 
 
 ipp. 86-87. 
 
 2 A substance pressed against the back of the nostril can hardly be 
 smelled at all, as its vapor will take the direct path to the choana. 
 
24 GAMBLB : 
 
 We naay say, then, that the most unsatisfactory features of 
 Zwaardemaker's method are (i) the adhesion-error, and (2) a 
 tendency which the subject, if he manipulates the odorous 
 cylinder, has toward judging in terms of hand-movement. 
 This difficulty will be discussed in another place. 
 
 While the intensity of the stimulus depends in the case of 
 any sense upon the condition of the peripheral organ, no sense- 
 organ is so likely to vary either through obstruction or through 
 exhaustion as is the organ of smell. I^et us now consider the 
 variations from the normal condition to which this organ is 
 most subject. 
 
 Section 3. Anosmia and Hyperosmia} 
 
 Whether pathological or non-pathological in origin, anosmia 
 is of three sorts, — respiratory, essential or toxic, and nervous. 
 Respiratory anosmia is due to obstruction of the nasal passages, 
 from asymmetry of the nasal skeleton, from hyperaemia of the 
 respiratory or Schneiderian membrane, or from accumulation of 
 mucus. Toxic anosmia may be due to poisons in the inspired 
 air, — a form not yet investigated, — to injurious fluids introduced 
 directly into the chamber containing the sense-epithelium (as 
 in Aronsohn's experiments), to poison^ such as morphine, 
 pulverized and blown into the nose, or to certain forms of 
 blood-poisoning, such as chronic nicotine-poisoning. The 
 anosmia of smokers cannot be wholly attributed to their 
 catarrh, though a light, acute nicotine-poisoning does not 
 seem to produce a loss of smell. Nervous anosmia may be 
 congenital, — /. e. , due to imperfect development of the olfac- 
 tory vesicle in the brain, — or may be senile, — due to degenera- 
 tion of some of the nervous elements which condition the 
 sense, — or may be due to exhaustion of the olfactory nerve, 
 or to dryness of the epithelium. If we rule out exhaustion, we 
 may say that respiratory anosmia is vastly more common than 
 toxic or nervous. The more peripheral parts of every sense- 
 organ are more subject to injury and disease. Thus, the mus- 
 cles and lenses of the eye give much more trouble than the 
 retina and the optic nerve. In the case of smell, the sensory 
 epithelium is well protected by its secluded position. 
 
 As to hyperaemia of the respiratory mucous membrane, its 
 blood supply is controlled much more by the exigencies of 
 breathing than by those of smell. It is largely under the sway 
 of local reflexes. The fibers of the trigeminus which ramify 
 through it are closely connected with fibers of the sympathetic 
 nervous system. Too profuse secretion of mucus is the most 
 common mechanical hindrance to smell. On the other hand, 
 
 ipp. 136-165. 
 
WEBER'S LAW TO SMELL. 2$ 
 
 too small a secretion has a disastrous effect on the sense- 
 epithelium. It seems that the tiny hairs of the rod-cells re- 
 fuse to do their work if they become dry. The action of all 
 the mucous glands of the nose may be increased by injecting 
 strychnine, and decreased by injecting atropin into the mem- 
 branes. Too much atropin, however, produces irritation and a 
 flow of tears. 
 
 Hyperosmia may also be respiratory, — due to certain asym- 
 metries of the skeleton or to anaemia of the respiratory mem- 
 brane,— or toxic, or nervous. In hysterical subjects, hyper- 
 osmia is common. Anaemia of the respiratory membrane may 
 be produced by smelling such substances as cocoa-butter, or 
 cedar-wood, which rather powerfully affect the trigeminus. 
 
 The two forms of anosmia, which vary in the same subject from 
 day to day, are respiratory anosmia from obstruction of the nasal 
 passages by mucus, and nervous anosmia from exhaustion. It 
 is possible at any time easily to discover whether the nasal 
 passages are obstructed or not. The test can be made by ex- 
 haling on a concave metal mirror held at the level of the 
 mouth. The clouds of condensed vapor give the true shape of 
 transverse sections of the breathing-cones. They are divided 
 from each other, and if the nasal passages are in a normal con- 
 dition, they are symmetrical, and broader than they are long. 
 As they pass away, they should each divide into an antero- 
 medial and a postero-lateral division of about the same size. 
 As divided, the spots should still be roughly symmetrical. The 
 division is due to the projection of the "triangular cartilage " 
 and the lower turbinal bone from the side wall of the nose. 
 This division of the air current occurs in all mammals.^ Patho- 
 logical alterations in the raucous membrane of the nose and 
 asymmetry of the nasal skeleton may alter the size and shape 
 of these divisions, but rarely prevent them from appearing. 
 The antero-medial division alone represents the current of air 
 which passes above the lower turbinal bone. The form and 
 position of the field of smell in an ordinary inspiration, there- 
 fore, corresponds roughly with this division, and would do so 
 exactly if it were not for the slight difference in the course of 
 the currents of inspired and expired air.'' 
 
 The influence of exhaustion is more insidious. It varies 
 from subject to subject, from substance to substance, and from 
 one intensity of a substance and one general condition of a sub- 
 ject to another, so that numerical corrections are out of the 
 question. Fortunately or unfortunately, the effects of adhe- 
 sion and exhaustion are for the most part opposite. This 
 
 ^P. 73- 
 ^Pp. 73-74- 
 
26 GAMBLE : 
 
 Opposite influence makes one's numerical results more nearly 
 correct than they would otherwise be. On the other hand, it 
 makes the exact influence of each source of error more difficult 
 to read from the figures. Yet it is not particularly difficult to 
 detect the efiect of the exhaustion when it is at all marked, and 
 to exclude the most unreliable determinations. In our expe- 
 rience of thirteen different subjects, complete or marked 
 anosmia from exhaustion, if it occurred at all, usually came on 
 very suddenly. 
 
 Section 4.. Psychophysical Methods Employed. 
 
 Before difference-determinations were made at all, the stim- 
 ulus-limen was usually found as accurately as possible for the 
 substance and subject concerned. The subject, starting with 
 the end of the odorous cylinder even with the end of the inhal- 
 ing-tube, moved the cylinder outward until he obtained a smell. 
 If this smell seemed to him more than liminal, he moved the 
 cylinder back for a short distance, and continued to move back- 
 wards and forwards until he had satisfied himself as to the point 
 at which he obtained a just noticeable sensation. The method 
 of moving steadily in both directions, — from a point considera- 
 bly below to a point just above the limen, and from a point con- 
 siderably above to a point just below the limen, — was tried, but 
 was abandoned. It is often impossible, on account of adhesion 
 in the tube or in the nasal passages, or on account of memory 
 after-images, or cumulative stimulation, to move from a point 
 of intensive stimulation to a point at which sensation entirely 
 disappears. Memory after-images certainly occur." The exist- 
 ence of true after-images of peripheral origin has not been 
 proved in the case of smell. ^ 
 
 The only difference- determinations for smell, so far on record, 
 are a few which Zwaardemaker performed for yellow wax and 
 vulcanized rubber. The method which he employed,- and the 
 method which so far seems practicable, is Fechner's rough and 
 simple method of just noticeable differences. One gives the 
 subject a standard stimulus, and then after an interval, which 
 one makes as nearly uniform as possible, a second stimulus 
 which is appreciably greater or smaller. He himself then 
 moves the cylinder until he makes the stimulus just greater 
 or just smaller than the standard. When in the neighborhood 
 of the ntimuluo , he moves back and forth as he likes, until he 
 has satisfied himself of the accuracy of the determination. 
 Thus, as there is near the limen procedure in both directions, 
 the method may be classed as a gradation-method. The in- 
 terval between the two stimuli averaged in our experiments 2j^ 
 
 , 1 P. 260. 
 
WEBER'S LAW TO SMELI,. 27 
 
 seconds with the standard olfactometer, and 5 seconds with the 
 fluid-mantle olfactometer. With the small olfactometer, it was 
 never less than 2, and almost never greater than 4 seconds. It 
 was ordinarily 2. With the large olfactometer, it varied from 
 4 to 6 seconds. The difficulty in manipulating the large olfac- 
 tometer more quickly will be described in another place. The 
 interval between determinations was much more variable. It 
 was usually about a minute, except when the tube was cleaned. 
 Our determinations were broken into short series in which 
 Aro and Arw were found alternately. The series were divided 
 from each other by the necessary cleanings of the inhaling- 
 tube. With some substances, we washed and dried the tube 
 after every 8 determinations, wiping it out with dry absorbent 
 cotton in the middle of the series. ' With other substances, we 
 washed and dried it at the end of every 4 determinations. It 
 took about a minute to give the tube a dry wipe, making the 
 interval between half series about 2 minutes. After practice, 
 it took about 3 minutes to wash, wipe and dry the tube, mak- 
 ing the interval between series about 4 minutes. These time 
 estimates are all rough. We were not intent on time-determi- 
 nations ; the subject had often incidental remarks to make on 
 his own experiences ; and there were various untoward acci- 
 dents, — water spilled, tubes broken, wire dropped, etc. The 
 subject used his two nostrils alternately ; all our records were 
 kept for the two nostrils of each subject as for two different 
 persons. We changed the order of determinations in successive 
 series that exhaustion and adhesion might equally affect A»-o 
 and Aru for the right nostril and for the left. For example, 4 
 series might run thus : 
 
 (i) Aro f. R. N., Aro f. L. N., Aru f. R. N., Aru f. 1. N. 
 
 (2) Aruf. 1,. N., Aruf. R. N., Aro f. L. N., Aro f. R. N. 
 
 (3) Aruf. R. N., Aruf. L. N., Aro f. R. N., Aro f. L. N. 
 
 (4) Aro f. L. N., Aro f. R. N., Aruf. I,. N., Aru f. R. N. 
 
 With the standard olfactometer, after some practice in clean- 
 ing the tube, we took usually 32 determinations in an hour ; 
 with the fluid-mantle olfactometer, 24. It was not worth while 
 to take more even if there was time, as the effect of exhaus- 
 tion became too marked. Fortunately, the odors of the solids 
 used with the small and easily handled olfactometer, were less 
 exhausting than the insistent smells of most of the solu- 
 tions. 
 
 With an unpracticed subject, we used one standard a day. 
 With a practiced subject, we took determinations first with a 
 weaker, then with a stronger standard on the same day. If 
 the substance was very exhausting, we worked first with a 
 weaker, then with a stronger, then with a weaker, then with a 
 
28 • GAMBLE : 
 
 Stronger standard. The subject was always warned of a change 
 in the standard. 
 
 Two grounds of objection to the method of just noticeable 
 differences are mentioned by Wundt. They are the haphazard 
 choice of the more intensive stimulus, which may light upon 
 a stimulus unnecessarily large, and thus weary the subject's 
 attention and sense-organ unnecessarily, and the irregularity 
 and immeasurability of the moving back and forth in the 
 vicinity of the difference-limen, — the " Tatonnieren. " It 
 should be noted, however, that as exhaustion increases during 
 the act of determination, A ro would always be too large and A ru 
 too small, were it not that adhesion has a precisely opposite 
 effect, which is increased by the time-error. Thus, there is 
 really a rude double cancelling of errors. 
 
 The true method of minimal changes involves great practi- 
 cal diflSculties if applied to difference-determinations with 
 Zwaardemaker's olfactometer. On account of the adhesion in 
 the inhaling-tube, either two olfactometers must be used, and 
 both inhaling-tubes cleaned after every comparison of two 
 stimuli, or only such substances must be used as are insoluble 
 in water and do not condense on the inner surface of the in- 
 haling-tube. Zwaardemaker tried the method with vulcanized 
 India-rubber, and believes it to be practicable for this sub- 
 stance.^ We, too, tried it with the tube of red vulcanized 
 India-rubber sent from Holland, and obtained very satisfactory 
 results. (See Table VIII. ) 
 
 We also tried a combination of the two methods mentioned. 
 Giving the subject a variable stimulus objectively equal to the 
 standard, we bade him make it subjectively equal, — for it 
 would tend to seem subjectively less from the effect of exhaus- 
 tion, — and then after pausing to let us take the reading, to 
 make it subjectively just greater than the standard. Then he 
 was directed to make a variable stimulus very appreciably 
 greater, just equal subjectively. Next, after making an ob- 
 jectively equal stimulus subjectively equal, he made it sub- 
 jectively less. I,astly, he ma'de an appreciably weaker stimulus 
 subjectively equal to the standard. Some of the results obtained 
 by this method are given in Table VII. They are arranged 
 in connection with results obtained for the same subject, sub- 
 stance and standard by the method of just noticeable differ- 
 ences. The uncertainty of a method in which the subject 
 exhausts an already wearied organ by hunting for subjective 
 equality before proceeding to the determination proper, is 
 obvious. Therefore, the two sets of results tally surprisingly 
 well. 
 
 1 Pp. 189-190. 
 
WEBER'S LAW TO SMELL. ' 29 
 
 Witli any form of the method of just noticeable differences 
 in which the subject himself alters the stimulus of comparison, 
 there is liability to serious error from the subject's inclination 
 to judge in terms of movement. When he has found that a 
 certain hand-movement has made the stimulus of comparison 
 just noticeably greater or less than the standard, he will expect 
 the same movement to make it just noticeably greater or less 
 again. He will be all the more tempted to judge in terms of 
 hand- movement from the fact that he has been all his life form- 
 ing estimates of space in terms of the sensations produced by 
 movement, and has probably never thought of taking pains to 
 compare the intensity of two odors. This tendency varies 
 much in different subjects. Its presence may be suspected 
 when the mean variation of a series is very small. Fortunately, 
 it acts in such a way as rather to conceal the operation of 
 Weber's law, if applicable, than to make it appear applicable 
 if it were not. If, for example, one finds A r to be 5 mm. for a 
 standard of 20 mm., and by repeating the series of movements, 
 obtains the same value of A r for a standard of 40 mm., Ar will 
 
 r 
 be % in the one case, and yi in the other. 
 
 As a matter of fact our results offer evidence for the law 
 which is strong to an almost suspicious degree. Yet it is not 
 probable that a trained subject would, or that an untrained 
 subject could deliberately alter his movements, when the stand- 
 was varied, so as to keep the value o f Ar approximately the 
 
 r 
 same, and it is absolutely impossible that twelve subjects out of 
 thirteen should all do so. Such a procedure would argue a 
 miraculous combination of psychophysical knowledge, accurate 
 memory, industry and malice. 
 
 We also made some attempt to test the applicability of the 
 method of right and wrong cases. At the time we tried it, 
 which was early in the course of our experiments, we found it 
 utterly impracticable. The fact that more than half the mis- 
 takes were made in thinking the second stimulus weaker than 
 the first or equal to it, would indicate that exhaustion was the 
 disturbing factor. Since, however, the subject seems genuinely 
 to recognize the stimulus of comparison in the gradation- 
 methods as greater or less than the standard, it is probable that 
 the difficulty with the- method of right and wrong cases is 
 largely the utter confusion it produces in his mind. Most 
 persons are not used to smelling attentively and have to 
 ' ' learn ' ' a given smell-intensity. 
 
30 GAMBLE : 
 
 Chapter II. Apparatus and Materiai<s. 
 Section i. The Standard and Fluid-Mantle Olfactometers. 
 
 In our experiments, we employed the single "standard" olfac- 
 tometer and a double form of the ' ' fluid-mantle ' ' olfactometer. 
 Both instruments were supplied from Utrecht. The sliding 
 tubes used with the standard or small olfactometer were formed 
 of the odorous material itself, and covered with an outer tube 
 of glass. Porcelain cylinders, saturated with odorous solu- 
 tions, and fitted into larger glass tubes, have been largely used 
 by Zwaardemaker in connection with this simple instrument. 
 We, however, used the porcelain cylinders only with the large 
 or fluid-mantle olfactometer. "We shall reserve the considera- 
 tion of the preparation of the odorous substances to the next 
 section. Here we shall describe the screen and inhaling-tube 
 of the small instrument, and all the appurtenances of the large 
 instrument, except the odorous solutions. 
 
 /. Standard Olfactometer. The glass inhaling-tube has a total 
 length of 15 cm. and a bore of 5 mm. The glass varies in different 
 tubes from i to \}i mm. in thickness. The portion which curves up- 
 ward to fit into the nostril is never more than i^ cm. long. Zwaar- 
 demaker says that the angle of the bend seems to make no difference 
 with the results of the experiment. He himself makes it a right an- 
 gle, but Renter makes it an angle of 40 degrees.^ A metal sleeve 
 carrying a raised bead at the edge towards the bent end of the tube 
 and buttoning into a metal ring in the center of the small wooden 
 screen is fastened to the tube in such a position as to allow 10 cm. to 
 project beyond the screen. This portion is graduated into twenty 
 divisions of 5 mm. each. The securing of the metal to the tube is a 
 serious problem in practice. We were able to find neither odorless 
 glue nor cement which would withstand the constant washing of the 
 tube, and the drying over the spirit-flame, a performance which must 
 be repeated from four to a dozen times in a single hour. We finally 
 solved the difficulty for ourselves by pasting with freshly dissolved 
 gum arable a strip of paper to the tube, and working the metal ring 
 down over it, where it fitted so tightly as not to be removed without a 
 process of soaking. The graduated tubes can be easily duplicated by 
 any glassware firm.^ They are so frequently broken in cleaning by 
 an unpracticed operator, that no extended course of experiments 
 should be undertaken without laying in a stock of them. 
 
 The screen is a square bit of cherry wood, — 7^ cm. broad by 10 cm. 
 high by i cm. thick, — furnished with a handle and ^coated with var- 
 nish which is supposed to be odorless. The screen must, however, be 
 freely exposed to the air, and when new, must be well sunned, or it 
 will have a decided smell of its own. Its double purpose is to serve 
 as a handle, and toprotect the nostril not in use from the odor of the 
 sliding cylinder. The subject in making his determination holds the 
 handle of the screen in his left hand and moves the cylinder with his 
 right." 
 
 ip. 104. 
 
 2 Messrs. Eimer and Amend, of New York, courteously duplicated 
 for us all of our imported tubes. 
 *The standard olfactometer can be made in any laboratory. See the 
 
WEBER'S LAW TO SMELI,. 3 1 
 
 ' //. Fluid-Mantle Olfactometer. In this instrument, the constant 
 saturation of the hollow porcelain cylinder is secured in the following 
 manner : A section of wide glass tubing is secured between two cir- 
 cular and cork-lined end-plates of metal. One of the metal plates,— 
 that which when the instrument is adjusted is nearer to the subject, 
 —IS furnished with three equidistant rods, inside of which the disks 
 of cork and the glass tube fit. The three rods terminate in three 
 screws with detachable heads. The screws pass through holes in the 
 other metal plate. The plates are bored at the center to circular open- 
 ings, 8 mm. in diameter, which coincide with the bore of the enclosed 
 porcelain cylinder. The cylinder itself, which has exactly the length 
 of the glass tube, — lo cm., — is held in place simply by the pressure of 
 the end-plates. The glass inhaling-tube passes through the screen 
 into the bore of the cylinder. The odorous solution is put into the 
 space between the cylinder and the glass tube with a pipette through 
 one of two holes, 2 mm. in diameter, which are left one in each of the 
 two metal plates, and closed with cork-lined screw-heads. It would 
 be better if there were two of these holes in each plate, for it is ex- 
 tremely difficult to force a sluggish liquid, such as glycerine, against 
 the pressure of the air into the space around the cylinder. If the 
 rubber of the pipette is flaccid, it becomes almost impossible. 
 
 The " shells " thus constructed for mantling the cylinder with 
 liquid, are mounted in a horizontal position on a wooden table, — 27.7 
 cm. long by 16.4 cm. wide, — which can be adjusted to the required 
 height above a heavily leaded base. Each of the shells can be 
 moved to and from the observer along a way of hard wood. The rack 
 and pinion movement is governed by milled heads, — diameter 2^ cm., 
 — projecting from the table to right and left within easy grasp of the 
 subject's hand. A scale and pointer enable the observer to determine 
 how far the cylinder is moved. 
 
 The inhaling-tubes are made with the same bore an.d of glass of the 
 same thickness as the graduated tubes used with the standard olfactom- 
 eter. Those sent from Holland turn, one to the right and the other 
 to the left before curving upward to be inserted in the nose. The 
 metal sleeves, within which the tubes are cemented, do not bolt into 
 the holes in the screen, but flare off each on its outer side into flat fan- 
 shaped pieces of metal, which are screwed to tally with a mark on the 
 screen. We made no experiments with these tubes, but used instead 
 tubes of the same bore and thickness of glass, either with a somewhat 
 shorter upright, or with but one curve. The tubes with one curve are 
 precisely like the inhaling-tubes of the standard olfactometer, except 
 that the part which extends through the screen is longer and is not 
 graduated. It is a mistake to use two-jointed tubes at all, unless both 
 nostrils are to be used, as in compensation-experiments. The extra 
 curve seems to make no difference in the results, but it makes the 
 tubes much harder to clean. The total length of our two-jointed 
 tubes was iB}i cm., and that of our one-jointed tubes, IT% cm. XI.3 
 cm. of every tube used must project beyond the screen. We fitted 
 our tubes into hollow plugs of cherry wood turned to order in the 
 shape of corks, so as to pass easily into the holes of the screen, and 
 
 directions given in Sanford: Experimental Psychology, p. 371. Scrip- 
 ture's blotting-paper olfactometer as, made b;^ Willyoung, is rendered 
 useless by the vulcanized India-rubber of the inhaling-tubes. We sub- 
 stituted for the inner glass-tube, rubber-tube, and nose-piece, a glass 
 tube bent at right angles and expanded into a nose-piece at its upper 
 end. The dimensions of this tube, however, make it very breakable, 
 and it is quite impossible to clean it except by blowing through it. 
 
32 GAMBLE : 
 
 to fit tightly when pushed home. To keep the tubes themselves from 
 slipping backwards and forwards in the plugs, we gummed strips of 
 paper to the glass at the edge of the wood. Lumps of these strips 
 will continue to adhere even after many washings. These home-made 
 substitutes for the heavy metal attachments are very serviceable. 
 
 We should advise all who purchase the instrument to strengthen 
 the table with metal cross pieces on its under side. The upward 
 warping, which is inevitable, narrows the ways and throws the inhal- 
 ing-tube out of alignment with the porcelain cylinder. The result is 
 a stiff movement of the rack and pinion on the one hand, and a per- 
 petual breaking of - inhaling-tubes on the other. Moreover, if the 
 warping has gone far, the whole table is liable to split. We have also 
 found it necessary to shave the edges of the wooden blocks which 
 carry the shells, and to reduce the friction caused by two spring- 
 brakes placed alongside of the ways. It would be much better if the 
 carrying blocks were moved with cranks, rather than by the milled 
 heads. The exertion necessary to turn the screw and the chafing of 
 the hand by the milling are distracting to the subject's attention. 
 Moreover, the intervals when the experimenter is turning the head 
 to give the stimulus of comparison are undesirably long. Great care 
 must be used in the selection of any oil which is applied to the in- 
 strument. We once used clock oil, and afterwards had extreme 
 trouble in eradicating the odor. 
 
 The porcelain cylinders for these olfactometers are made by Hooft 
 and Labouchere in Delft, and composed of pure kaolin. They must 
 be kept continually immersed in water, and this must be removed at 
 least daily to minimize the odor of the clay. They must not be dried 
 before they are introduced into their glass coverings. The ends are 
 perfectly smooth, and are glazed for use with the standard olfactome- 
 ter. The outer and inner surfaces remain porous. All the cylinders 
 used, whether made of porcelain or of the fragrant material itself, 
 have a length of lo cm., and a bore of 8 mm., so as to slide easily 
 along the inhaling-tube, and to cover, in case of the standard olfactom- 
 eter, the graduated portion of the tube lying beyond the screen. 
 The external diameter, — counting the thickness of the protecting 
 shell of glass, when present, — varies from 14 to 16 mm. 
 
 Section 2. Preparation of Odorous Materials. 
 
 In Table VI (Chapter III, Section 2) the odorous materials are 
 arranged in their order according to Zwaardemaker's scheme 
 of olfactory qualities. We shall here describe them in groups 
 according to their mode of preparation. We shall consider first 
 the preparation of the tubes of solid odorous matter, and after- 
 wards discuss the solutions used to saturate the porcelain cylin- 
 ders. 
 
 /. Preparation of Odorous Substances Used in Solid Form. The 
 solid odorous materials from which tubes or hollow cylinders were 
 prepared were vulcanized India rubber, black, red, and gray ; cedar, 
 rose-wood and musk-root ; Russian leather, yellow wax, paraffine, glyc- 
 erine soap, mutton-tallow, cocoa-butter and solid oil of mace, asafost- 
 ida, gum benzoin, tolu balsam, and a combination of gutta-percha 
 and gum ammoniac in equal parts by weight. Tubes of red and black 
 India rubber, and of gutta-percha and gum ammoniac came with the 
 standard olfactometer from Utrecht. All the other cylinders, and a 
 second tube of gutta-percha and gum ammoniac, were home-made. It 
 is necessary that all such cylinders should be fitted into glass tubes 
 
wbber's law to smell. 33 
 
 of the same length in order that no odor from their outer surfaces 
 may pass around the screen. 
 
 India rubber has three great qualifications for use in experiments in 
 smell, (i) It can be smelled for a long time by most subjects with- 
 out blunting the organ ; (2) its odor is not easily obscured by other 
 odors, and (3) adheres comparatively little to the ihhaling-tube. Two 
 of our subjects (C and SA.), however, complained more of smarting 
 in the nose when using rubber than when using any other substance. 
 The age and mode of preparation of different sorts of rubber, and the 
 arnounts of sulphur in them, make some difference in the quality and 
 slight differences in the intensity of the smell. The intensity, is, on 
 the other hand, virtually the same at all degrees of temperature be- 
 tween 13° and 30° C. The cylinder may be prepared by cutting 10 
 cm. from a rubber tube with a bore of 8 mm., and working it into a 
 glass tube of the same length. The rubber must be clean and new, 
 and, in particular, must never have come in contact with illuminating 
 gas. Although the odor of the rubber when fresh is not easily dis- 
 guised by other smells, yet the substance easily loses its own odor 
 and takes that of other substances. An inhaling-tube or the broken 
 fragment of one should, therefore, be left in the cylinder so as to 
 cover its inner surface when not in use. Such tubes must never be 
 allowed to lie about unprotected on the shelves of a wooden cup- 
 board. If not sealed by containing the inhaling-tube, they should be 
 rolled up in clean glazed paper and shut up in a jar by themselves. 
 
 Our cedar and rose-wood cylinders were turned to order. A block 
 of wood 2^x2^x4^ ins. will make four of these tubes. Bach was 
 held in its place in the outer tube of glass by a small bit of "instant 
 crockery-mender" applied to the wood before putting it in. The fit 
 is so tight that the odor of the paste cannot escape. These cylinders 
 also are very liable to lose part of their odor, and should be carefully 
 protected. Messrs. McKesson and Robbins, of New York, furnished 
 a single piece of musk-root large enough to make two cylinders. One 
 crumbled in the turning, but the other broke evenly around the cir- 
 cumference into two sections, which were pushed so tightly into a 
 glass tube as to stay in place of themselves. The crack was almost 
 invisible, and as it was 6 cm. from one end of the tube, it did not ren- 
 der the cylinder really defective. Prom the Russian leather, — which 
 was genuine, and not the "Russian leather" of America, which is 
 tanned with birch instead of sandal wood, — a piece 24 mm. wide and 
 10 cm. long was cut, and was fitted into a tube so as exactly to cover 
 the inner surface. Cylinders may be prepared in the same way from 
 India rubber sheeting. 
 
 The other substances were all melted and moulded . The glycerine soap 
 was Pear's, the mutton fat employed was fresh from the butcher's, the 
 cocoa-butter, parafiane (the kind used by histologists), gum benzoin and 
 gum ammoniac were such as can be bougjht of any retail druggist. We 
 obtained of McKesson and Robbins " solid " oil of mace and the pure 
 juice of asafoetida done up in small tin cans, and also a quantity of 
 gutta-percha in narrow fibrous sticks or slabs, and of tolu balsam en- 
 tirely freed from impurities. For the outside mould, the permanent 
 glass shell must, of course, be used. The glass tubing was cut before- 
 hand in our case into lengths of 10 cm., and these moulds were corked 
 at one end, so that the tube of odorous matter was never quite 
 so long as its shell. For the inside mould, we used an inhaling-tube, 
 or the long straight part of one which had broken at the curve. The 
 tube may be kept upright by digging a hole for the end of it in the 
 cork. This end should be plugged to prevent the liquid from workmg 
 up into the tube, through which it is sometimes necessary to pour 
 
34 GAMBLE : 
 
 warm or cold water. All the odorous substances in this group were 
 melted in a water-bath. We crumbled or shaved them into a small 
 beaker, which we floated by means of a ring of cork in a large 
 beaker of water over a Bunsen burner. We tried to melt the gums 
 in a sand-bath, but succeeded only in charring them. The mass 
 which we obtained by melting the gum ammoniac and gutta-percha 
 together was of lighter color than that sent from Holland, and was 
 not entirely free from the fibres of the gutta-percha. It was spongy 
 and easily moulded by the fingers into any desired shape. The soap, 
 paraffine, cocoa-butter and tallow are readily manipulated. They 
 solidify in a very few moments if the outer tube is immersed in cold 
 water, and the removal of the inner mould presents no difficulty. 
 Tubes of these materials were kept all the summer in a room of which 
 the temperature occasionally rose to 94" P., and sustained no damage 
 by the heat. The tubes of soap, however, sometimes shrivel in a few 
 days independently of the temperature. The longer the paraffine is 
 heated the stronger the odor. Zwaardemaker succeeds in giving it an 
 odor as strong as that of tallow or musk-root. We did not try heat- 
 ing it longer than an hour and a half, and our paraffine tubes gave the 
 weakest of all our scents. Tubes of tallow are easy to make and to 
 keep, and do not exhaust the subject's sense-organ to any appreciable 
 extent, and are therefore especially to be recommended. 
 
 The oil of mace has a consistency like that of table-butter. It melts 
 rapidly, and solidifies almost instantly when the outer mould is 
 plunged into ice water, but tends to stick to the inner tube, and to 
 come out with it in perfect shape. To remove the inner tube by itself, 
 we filled it with ice water, and then hastily poured a little hot water 
 over the outer mould. When once made, the mace tubes should be 
 kept in a cool place, and the jar in which they stand should not be 
 set on end. While they are in use, they must be grasped only with 
 the tips of the fingers, and must be cooled every few moments with ice 
 or snow. The juice of asafoetida, when pure, never becomes solid 
 enough to be moulded. We poured small quantities of it, when 
 melted, upon a mass of pulverized carbonate of magnesia, and worked 
 the two materials together with our fingers, as one works flour into 
 a very soft dough. We put lumps of this mixture into an outer 
 mould, heated it in the water bath for a few moments, and then 
 forced the inner tube down through the mass as nearly parallel with 
 the outer mould as possible. After many attempts, we succeeded in 
 making several satisfactory cylinders. Their odor, in spite of the 
 adulteration of the asafoetida, is only too strong. 
 
 The gums never become very liquid in melting, and they solidify 
 almost instantly when removed from the heat. We found it difficult to 
 pour the gum benzoin, and impossible to pour the tolu and the mixture 
 of gutta-percha and gum ammoniac, into the space between the inner 
 and outer moulds. We poured this mixture and the tolu into the 
 outer tube when empty, and then forced the inner tube into its place, 
 as in the case of the asafoetida. When the fragrant substance is a 
 gum, this inner tube must be greased. We coated it rather thickly, 
 but evenly, with lanolene, which is as nearly odorless as grease can 
 easily be found, and which evaporates quickly. All these tubes of gum 
 retain their odors well, but the tolu is likely to melt out of shape in a 
 hot room. 
 
 Before these cylinders are used, the section of odorless substance 
 exposed at the outer end must be covered . We employed a little ring or 
 cap of glazed paper gummed to the surface. Even with this precaution, 
 the odor of the asafcetida, mace, butter and Russian leather, is quite 
 apparent when the instrument is closed by pushing the odorous tube 
 
WEBER S LAW TO SMELL. 35 
 
 as far in as possible. It apparently proceeds from such space as there 
 is between the inside surface and the inhaling-tube. The inhaling- 
 tube, on the other hand, must not fit too closely in the inside of the 
 odorous tube, for if it does, the subject will be able to move it only in 
 irregular jerks, and it will, moreover, scrape off shavings from the in- 
 side surface of a cylinder of soft material, such as asafoetida or oil of 
 mace. When it is used with the Russian leather, a bit of paper may be 
 gummed around it to make it fit somewhat more closely. Bven this, 
 however, does not keep the smell of the leather from making itself 
 apparent in the space from which one breathes through the tube. We 
 attempted to find "negative stimulus-limina " for the troublesome 
 substances, in the following manner : We used a graduated inhaling- 
 tube 4 cm. longer than the ordinary one, and adjusting the cylinder 
 over the lo cm. nearest the screen, moved out to find the limen. 
 The device was not successful. The odor still diffused itself through 
 the space from which the air was drawn. All the determinations of 
 difference-limina for these substances involve a constant error, — 
 namely, the addition of an increment, which we have no means of 
 measuring, to every stimulus represented on the tube. 
 
 //. Preparation of Odorous Substances in Solution. Of the odor- 
 ous substances used in solution, the caryophylline, citral, vanilline, 
 coumarine and heliotropine were among the "DeLaire Specialties," 
 and were, with the ethyl butyrate, tincture of musk, and oil of cam- 
 phor, the gift of Messrs. Dodge and Olcott, of New York. " The 
 De Laire products," writes a representative of Dodge and Olcott, 
 "are not an embodiment of the simple chemical formulas suggested 
 by their names. They are compounds after secret recipes, and their 
 names denote only the odor or flavor or other quality which it is 
 claimed they reproduce or imitate. De Laire's caryophylline, for 
 example, is not the caryophylline of your chemical formulas, a dis- 
 tinctly isolated aromatic principle, but a preparation, having doubt- 
 less as its base one of the clove-oil products, which is intended to 
 supply the perfumer with the bouquet of the clove-pink." We have 
 retained the De Laire spelling of their own specialties. The chemical 
 formulae of butyric ether, valerianic acid, allyl sulphide, and pyridin 
 are, respectively, Cj H5. C^ H, O^, C5 Hjo O2, (C, H5) S, and C5 
 Hj N. The butyric ether used was a commercial product, but the 
 valerianic acid was obtained at the chemical laboratory of the Uni- 
 versity, and the allyl sulphide and pyridin, as well as the oil of anise, 
 were had of the Theodore Metcalf Company, of Boston. 
 
 Our solvents, mixtures, and concentrations were as follows : 
 Oil of camphor in liquid paraffine, a mixture, 1:50° 
 
 Caryophylline in pure glycerine, a true solution, 1:500 
 
 Oil of anise in liquid paraffine, a mixture, i:i66% 
 
 Valerianic acid, in water, a true solution, 1:1500 
 
 Ethyl butyrate, " " " 1:1000 
 
 Citral, in liquid paraffine, " " 1:500 
 
 Vanilline, in pure glycerine, " " 1:125 
 
 Coumarine, in liquid paraffine, " " 1:1000 
 
 Heliotropine, in liquid paraffine, " " 1:125 
 
 Natural Musk, the ordinary alcoholic tincture, in water, 
 
 a mixture, 1:125 
 
 Allyl Sulphide, in liquid paraffine, a true solution, r:iooo 
 
 Pyridin, in water, a true solution, 1:500 
 
 Laudanum, the ordinary alcoholic tincture, a true solu- 
 tion, unmixed. . . , . . ,,.^. . 
 
 Some of the musk was of course precipitated by the addition of so 
 much water, and floated about in dark brown specks, a state of affairs 
 anything but desirable. 
 
36 GAMBi,E : 
 
 We are aware that all the concentrations are startlingly high. We 
 could not, however, use lower concentrations if we were to fix our 
 standard-stimulus in two places on the scale. With a few exceptions, 
 our stimulus-limina were much higher than those given by Zwaarde- 
 maker as normal. These facts will be noted later in detail. Zwaarde- 
 maker recommended vanilline in glycerine in the concentration of 
 i:iooo and coumarine and allyl sulphide in paraffine in the same con- 
 centration as especially well fitted for difference-determinations. We 
 did use the coumarine and allyl sulphide in these concentrations, but 
 most of our subjects obtained no odor whatever from the vanilline at 
 i:iooo, and in no case did the stimulus-limen fall for both nostrils 
 below 36 mm. 
 
 For coumarine, heliotropine and tincture of musk, stimulus-limina 
 were found in a satisfactory manner. With all the other substances, 
 an odor was apparent when the pointer of the fluid-mantle olfactom- 
 eter stood at zero. The odor, undoubtedly, came from the space 
 between the inhaling-tube and the inside of the porcelain cylinder, 
 as great pains had been taken to wash away every drop of liquid from 
 the metal plates. It is almost impossible so to adjust the inhaling- 
 tube that it will not scrape against the clay at some point, and to 
 paste paper around it would be out of the question, since the paper 
 would continually rub and wipe the odorous surface. The odor was 
 apiiarent 4 cm. from the end of the ordinary inhaling-tube when the 
 cylinder was supposed to be sealed. All the determinations of differ- 
 ence-limina for these substances also are, therefore, subject to a 
 constant error, but not so great an error as occurs in the results for 
 the troublesome solids with the exception of Russian leather. The 
 odor of the solutions when the instrument was closed was usually 
 barely liminal. 
 
 When water was used as a solvent, it was, of course, distilled. The 
 measuring-glasses and the bottles used should be rinsed well with 
 distilled water, or at least with water which has been freshly steril- 
 ized by boiling just before the liquids are poured into them. An 
 aqueous solution becomes unfit for use if long exposed to the light. 
 Zwaardemaker advises that the fluid-mantle of the porcelain cylin- 
 der be changed every two days. We usually not only changed the 
 mantle, but made a fresh solution, as often as this. It is safe to use 
 the same glycerine or parafline solution for days or even some weeks. 
 The glycerine is much more difficult to put into the receptacle than 
 the paraffine, and for citral and caryophylline it is not so able a 
 solvent. It is difficult, however, to obtain and keep liquid paraffine 
 quite free from a slight odor, somewhat pungent and somewhat like 
 that of vaseline. Alcoholic solutions are, of course, more or less 
 undesirable, as we have noted before. I f Ar were known to bet he 
 
 r 
 same for all qualities, there would be no objection to using such solu- 
 tions, but to assume that it is, is to beg one question at issue. We 
 could not manage the musk and the opium, however, in any other 
 form. 
 
 Section j. Other Arrangements and Appliances. 
 For cleaning the inhaling-tubes, one needs a funnel of which one 
 end is small enough to fit into the bore ; two small light vessels,— 
 tin cups are best, — for pouring water back and forth through them ; a 
 roll of absorbent cotton ; a piece of pliable brass wire ; some listerine ; 
 and a small alcohol lamp. After a tube is washed, it must be wiped 
 inside and out with absorbent cotton before it is dried more thoroughly 
 over the spirit-flame, else it will break. We used listerine occasion- 
 
wbber's law to smblIv. 37 
 
 ally as a deodorizer during a set of experiments, and always as a 
 disinfectant at the end of the hour. Its own odor is easily washed 
 away. As it takes some time for a porcelain cylinder to become 
 thoroughly impregnated with an odorous solution, it is convenient to 
 have test-tubes with tightly fitting corks, in which a number of cylin- 
 ders may be put to soak at the same time. Unless they can be kept 
 in a dark cupboard, it is well to wrap up these tubes in several plieS 
 of black calico. Bottles of yellow glass, such as perfumers recom- 
 mend for the safe keeping of heliotropine, might well be used for all 
 the solutions, but if they are not available, ^he ordinary bottles of 
 colorless glass can be wrapped up in black cotton cloth. The less 
 woolen cloth about the room, the better. We keep our solid cylinders 
 in "self-sealing" preserve jars. When the cylinder with its fluid- 
 mantle in place is not in use, the bore should be corked to keep the 
 inner surface from drying off. It may, indeed, be filled with the solu- 
 tion and corked when it is put away for some time. In this case, all 
 drops of liquid must be wiped out with absorbent cotton before the 
 experiments begin. If it seems likely that much odorous substance 
 has condensed on the inner surface, the whole bit of apparatus, glass 
 shell and all, may be immersed in water. Xhe bore should then be 
 filled for a few hours with the odorous liquid. 
 
 The walls of the room in which our experiments were made are 
 covered with oiled paper, and the floor is covered with oil-cloth which 
 has a coating of shellac. The room has at present this defect, that 
 when the wind blows in certain directions, it is impossible to create 
 through it a draft of air which does not pass first through a hall 
 frequented by students and therefore dusty, and by no means free 
 from odor. When the standard olfactometer was used, the subject 
 sat between the observer and the window, and at right angles to the 
 observer, so that the light shone through the graduated inhaling- 
 tube. When the fluid-mantle olfactometer was used, subject and 
 observer sat at right angles to each other at the end of a low table. 
 
 Chapter III. Results. 
 
 Section i. The Several Subjects and their Stimulus- Limina. 
 
 Individual variations in the sense of smell are so great that 
 it is necessary to preface a chapter on experimental results with 
 an account of the subjects. The following notes upon our sub- 
 jects in alphabetical order are thrown into "noun-form" for the 
 sake of brevity. 
 
 Be. (Dr. I. M. Bentley), a trained subject. 
 
 Organ impaired by acute catarrhal troubles and easily exhausted. 
 
 Breathing spots always blurred and ragged at the division lines,— 
 indicating a catarrhal condition of the membranes, — and never quite 
 symmetrical. . , .... 
 
 rX usually determined with one inspiration ; Ar determmed with 
 
 from 2 to 4 inspirations. 
 
 Movements of cylinder long'and slow, but few. 
 
 Position indicative of strain. 
 
 Bi. (Miss B. M. Bickham), a wholly untrained subject. General 
 physical condition ne\iTa.sthenic. , ,, , , , , „ 
 
 Organ twice operated on (in '95 and '96) for hypertrophy of the 
 
38 GAMBivB : 
 
 membranes. Superfluous portions removed from both sides. No 
 catarrh now apparent. 
 
 Breathing spots usually well-rounded and symmetrical with, neat 
 division lines. 
 
 r\ and Ar determined with but one inspiration. 
 
 Movements of cylinder rapid with little repetition. 
 
 Position indicative of strain. 
 
 C. (Miss M. H. Carter), a. partially trained subject. 
 
 Organ very easily exhausted. Membranes subject to sudden con- 
 gestions of blood and mucus upon nervous fatigue. Adenoid growth 
 as a child. (The growth was not cut away, but disappeared of itself.) 
 
 Breathing spots ragged, ill-defined, and almost never symmetrical. 
 
 Breathing during an experiment irregular and violent. Tendency 
 to sniff obstinate. r\ and Ar usually determined with i or 2 inspira- 
 tions. 
 
 Movements of cylinder rapid with little repetition. 
 
 Position indicative of much strain. 
 
 D. (Mr. S. J. Druskin), a partially trained subject. 
 Breathing spots perfect, as a rule. 
 
 r\ and l\r usually determined with i or 2 inspirations. 
 Movements of cylinder at first rapid and few ; after practice, tenta- 
 tive with noticeable repetition. 
 
 Position indicative of but slight strain. 
 
 K. (Mr. T. Kairiyama), a trained subject. 
 
 Organ much impaired by hay-fever and other catarrhal trouble. 
 
 Breathing spots fairly symmetrical as a rule, but ragged at the 
 edges: 
 
 r\ and Ar usually determined with i or 2 inspirations. Bxpiration 
 violent ("to clean out the smell "). 
 
 Movements of cylinder tentative but few. 
 
 Position indicative of but slight strain. 
 
 M. (Miss E. B. Macleod), a wholly untrained subject. 
 Breathing spots seldom quite symmetrical and never well defined. 
 No catarrh before the current winter. 
 r\ and Ar usually determined with i or 2 inspirations. 
 Movements of cylinder always irregular from want of practice. 
 Position easy. 
 
 N. (Mr. A. C. Nutt), a. partially trained subject. 
 
 Organ : Easily exhausted. Sensitivity somewhat higher on the 
 right side, as a rule. (The subject complained of "feeling left- 
 handed " on the left side.) 
 
 Postero-lateral half of left breathing-spot usually missing (a fact 
 showing chronic obstruction of the left inferior meatus). Both spots 
 ill-defined. 
 
 r\ and Ar determined usually with 2 or 3 inspirations. 
 
 Movements of cylinder slow and tentative with but little repetition. 
 
 Position indicative of strain. 
 
 P. (Mr. C. A. Perry), a. partially trained snhi^ct. 
 
 Organ much impaired by chronic catarrh. Diseased portions 
 removed from the lower turbinal bones on both sides. 
 
 Breathing spots rarely symmetrical. Secondary division quite 
 apparent in spite of the operation mentioned. Spots ill-defined. 
 
 r\ and A>' usually determined with one inspiration. 
 
WEBER'S LAW TO SMEI,!,. 39 
 
 Movements of cylinder slow and tentative with but little repetition. 
 Posttton indicative of but slight strain. 
 
 Rob. (Mr. E. P. Robins), a trained subject. 
 
 Breathing spots rarely symmetrical or perfectly defined. 
 
 r\ and Ar almost invariably determined with one inspiration. 
 
 Movements of cylinder slow and tentative with but little repetition. 
 
 Position indicative of but little strain. 
 
 Reg. (Miss L. R. Rogers), a. partially trained subject. 
 Breathing spots rarely symmetrical or very well defined. 
 r\ and Ar usually determined with 2 or 3 inspirations. 
 Movements of cylinder slow with much repetition. 
 Position indicative of but slight strain. 
 
 Se. (Mr. W. B. Secor), a trained subject. 
 
 Organ : Sensitivity somewhat higher on the right side as a rule. 
 
 Postero-lateral half of left breathing spot usually very small or 
 missing as with N. Spots ill-defined. 
 
 rX and A^ usually determined with 2 or 3 inspirations, movements 
 of cylinder slow with some repetition. 
 
 Position indicative of strain. 
 
 Sh. (Dr. Stella E. Sharp), a trained subject. 
 
 General physical condition neurasthenic. 
 
 Organ easily exhausted. 
 
 Right breathing spot usually larger than left, edges of both spots 
 clearly cut. 
 
 r\ and A>' usually determined with one inspiration, movements of 
 cylinder slovi with little repetition. 
 
 Position indicative of much strain. 
 
 T. (Dr. Ellen B. Talbot), a trained subject. 
 
 Organ somewhat easily exhausted. Portions of both lower turbinal 
 bones removed to prevent congestions of mucous in the upper passages. 
 Sensitivity somewhat higher on the left side. 
 
 Breathing spots well rounded and clearly cut. Secondary divisions 
 imperfect. (When the nasal passages were clear the division was 
 represented only by indentations at the edges of the spots.) 
 
 r\ at first determined with one inspiration ; later in the work, with 
 2, 3, or even 4 as a more satisfactory procedure. Ar usually deter- 
 mined with 2 or 3 inspirations. 
 
 Movements of cylinder very slow and cautious with much repeti- 
 tion. 
 
 Position indicative of but little strain. 
 
 In the notes just given a subject is called "trained " if he had had 
 a fair amount of experience in general introspection. Only Be. had 
 had any training in smell-experiments before the beginning of the 
 course described in this paper. Some months earlier we had made a 
 futile attempt :to find his difference-limen with the weaker Utrecht 
 cylinder of gutta-percha and gum ammoniac by the method of minimal 
 changes. A subject is called '■ partially trained " if he began psycho- 
 logical laboratory-work about the time when these experiments com- 
 menced. The word "repetition" is used in connection with the 
 manipulation of the cylinder to denote the moving backwards and 
 forwards at the limen. 
 
 The breathing spots of all the subjects varied much from day to 
 day. Sometimes they were broken up into several bands, always run- 
 ning rather from front to back than laterally. Often one narrow 
 
40 GAMBLE : 
 
 medial strip would separate from one or the other. In most cases a 
 more or less jagged and blurred outline showed the adhesion of 
 clots of mucous to the passage-walls. In fact, twelve out of the thir- 
 teen subjects had suffered or were suffering from frequent " colds " 
 or from hypersecretion more or less chronic. As a function of the 
 turbinal bone is to deflect a part of the inspired air to the upper 
 passages, its removal damages the sense of smell. The sensitivity of 
 T'.was higher on the left side of the nose, from which, as she reported, 
 the smaller amount of bone had been taken, but the small remains of 
 the secondary division of the breathing spots did not indicate that 
 more bone had been removed on the one side than on the other. The 
 obstruction of the inferior meatus would not, iij itself, do much mis- 
 chief to the sense, but it must indicate a dropping of mucous from the 
 upper passages. It is of some interest to note that the subject (£>.) 
 whose spots are most perfect is a Russian. He came, however, to live 
 in New York city at the age of twelve. K. is Japanese, but has been 
 long enough in this country to suffer severely from the catarrhal cli- 
 mate. Rob., one of the best subjects, comes from Prince Edward's 
 Island. The homes of the other ten are scattered over the States from 
 Eastern Massachusetts to California, though none are farther south 
 than Missouri.^ 
 
 When it is said that A'' was determined with one, two,or more inspi- 
 rations, it is meant that the stimulus of comparison was manipulated 
 during one, two, or more inspirations. More than one inspiration was 
 almost never taken to " learn " the standard. It seemed better to risk 
 the increase of adhesion by allowing a subject to take as many breaths 
 to a determination as he wished than to make him try to form a judg- 
 ment when the force of an inhalation was decidedly on the wane. 
 Many of the subjects considered a judgment with one inspiration an 
 impracticable ideal. Z>., K., Se. and Sh., and in a smaller measure 
 Be. and P., had a bad habit of suspending an inspiration, and not of 
 sniffing, but of " holding the breath " momentarily during an inspira- 
 tion. This practice must have tended to weaken the stimulus by 
 allowing the air in the upper chamber to rush downwards to the mid- 
 dle meatus. Be., N., P., Rob., Se. and T. noticed that the stimulus 
 was stronger during the latter part of an inspiration. This may point 
 to cumulative stimulation of the rod-cells, or it may merely mean an 
 access of attention and an unconscious sniff. Se., who had the habit 
 of suspending an inhalation, noticed the increase most after a strong 
 inspiration, and D., K. and Sh., who had the same habit did not 
 notice it at all. And it is clear that this peculiar mode of breathing 
 would tend to prevent cumulative stimulation. On the other hand. 
 Be., P. and T. noticed the increase most when the stimulus was near 
 its limen, and this looks as if it were a matter of attention and breath- 
 ing-rate, especially as T. did not hold her breath. Be. remarked that 
 the least difference of attention altered the stimulus. Rob. thought 
 the first part of an inspiration gave the fairest measure of an inten- 
 sity, and Be. and Se. relied on it " in easy judgments," but judged by 
 the latter part of the inspiration if the stimulus were weak or vague. 
 N. and P. asserted that they judged "by the impression as a whole," 
 but N. confessed to a tendency " to emphasize the last whiff." T. re- 
 versed the procedure of Be. and P., usually judging by "the last 
 whiff," but repeating the inspiration and relying on the first impres- 
 sion if the determination were difficult. With Rog. exhaustion often 
 supervened in a long inspiration. If is clear that if the intensity of 
 
 ^Spraying the subject's nose at the beginning of the hour might be 
 a useful expedient, but we did not try it. 
 
wkber's i<aw to smell. 41 
 
 a stimulus alters -witli the duration of an inspiration as well as with 
 the manipulation of the instrument, the subject must make more than 
 one inspiration to determine a limen, unless the judgment is very 
 easy. It is probable that the first part of the inspiration, before the 
 smell "blossoms out," gives the best criterion of the intensity of a 
 stimulus. We would suggest that cumulative stimulation of smell 
 would be a profitable subject of investigation. 
 
 In an effort to smell with the standard olfactometer, C, D., K., P., 
 Rob., Rog., Sh. and T. all tipped the head to the left if using the 
 left nostril, and to the right if using the right, pointed the outward 
 end of the inhaling-tube in the same direction as the head was tipped, 
 and slanted the screen in the opposite direction. This odd uniformity 
 is perhaps explicable. On entering the nose the air ordinarily streams 
 a little toward the septum and the opposite directions in which the 
 subject slanted his head and the screen tended on each side to throw 
 the opening of the nose-piece into an acute angle with the septum, 
 while the turn given to the instrument in the horizontal plane threw 
 the opening a little toward the front of the nose.'' On the other hand, 
 Se. exactly reversed these directions on each side, and so did Be., ex- 
 cept that he turned the tube to point in the same direction as the 
 screen was slanted, so throwing its inner opening towards the back of 
 the nose. Bi. slanted both head and screen to the right when using 
 the right nostril, and to the left when using the left. This was prob- 
 ably a mere matter of attention to one nostril or the other. She was 
 not consistent in the pointing of the tube. N. turned everything to the 
 right. Unfortunately, no written notes were taken of the hand used, 
 but it was usually the right, the hand farther from the experimenter. 
 All the subjects tended to tilt the hand forward and the screen back- 
 ward, — probably in their desire to get " nearer " the stimulus. Almost 
 all, unbidden, closed their eyes. 
 
 T. once mentioned verbal associations as an aid in memorizing the 
 stimulus. This expedient was not common, ^if. wrinkled his_ fore- 
 head and nose in a marked degree, and once noted a tendency to judge 
 in terms of strain, especially about the eyes. Some substances were 
 pungent to a disturbing extent to every one, but C. and D. com- 
 plained much of "pain" from odors which no one else thought 
 pungent. D. explicitly distinguished the sensation from pressure. 
 He thought coumarine both pungent and " sour." Both C. and 
 D. said that they received simply sensations of pressure from 
 some stimuli. With D. sensations of smell merged in_ sensa- 
 tions of pressure as the organ became exhausted. C. said that 
 when she tried to smell the black rubber with the left nostril she 
 merely felt as if she were " breathing a feather," or as if the inside of 
 her nose were "pressed with a soft wad." Yet the judgments made 
 with this nostril agreed pretty well with those made with the other. 
 Be. occasionally spoke of sensations of pressure or pain from the 
 stimuli. Most of the subjects expressly denied temperature-associa- 
 tions. Be., however, said that tolu and heliotropine were cold; M. 
 that cocoa-butter was cold ; Rob. that vanilline was cold ; and N. that 
 white tallow and musk-root were warm, and camphor cold, and that 
 every smell grew warmer as it grew stronger. He thought of helio- 
 trope as "warm, dark and deep," in contrast with ylang ylang, which 
 was " light and fluffy." , . . . j j r ^u 
 
 The comparative sensitivity of the subjects may be judged from the 
 
 following Table : 
 
 5*i> -^.a^i, -v"- a- 
 
42 
 
 GAMBLE : 
 
 Table I. A Tabi,b of Stimulus-Limina. 
 Part I. Stiinulus-Limina Arranged to Show Individual Variations. 
 
 SUBSTANCE. 
 
 Nostril. 
 
 Be 
 
 Bi. 
 
 c. 
 
 D. 
 
 L 
 
 M. 
 
 H. 
 
 P. 
 
 BOt. 
 
 E0£. 
 
 SB. 
 
 SL 
 
 T. 
 
 I 
 
 
 
 M 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm 
 
 Mm. 
 
 Black rubber, 
 
 R. 
 
 36 
 
 
 4 
 
 (22) 
 
 (43.) 
 
 (35) 
 
 12 
 
 
 (6i> 
 
 I 
 
 (12) 
 
 7 
 
 (38) 
 
 
 
 L. 
 
 34 
 
 
 5 
 
 (23) 
 
 (59) 
 
 
 II 
 
 
 (50) 
 
 I 
 
 (23) 
 
 10 
 
 (30) 
 
 
 Gray rubber, 
 
 R. 
 
 9 
 
 (35) 
 
 
 I 
 
 
 (19) 
 
 
 
 
 (I) 
 
 5 
 
 (7) 
 
 
 
 
 L. 
 
 8 
 
 (29) 
 
 
 6 
 
 
 (22) 
 
 
 
 
 (I) 
 
 9 
 
 (.10) 
 
 
 
 Red rubber, 
 
 R. 
 
 L. 
 
 
 
 
 
 
 
 
 
 
 (I) 
 (0) 
 
 
 (4) 
 (5) 
 
 
 7 
 
 Russian leather, 
 
 R. 
 
 Iv. 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 
 
 10 
 
 ParafBne, 
 
 R. 
 
 
 
 
 
 
 
 
 
 
 12 
 20 
 
 
 (21) 
 (14) 
 
 
 10 
 
 Rosewood, 
 
 R. 
 L. 
 
 
 
 
 
 6 
 8 
 
 
 8 
 7 
 
 (54) 
 
 (67) 
 
 
 
 3 
 II 
 
 
 
 3 
 
 Cedar, 
 
 R. 
 
 
 
 (4) 
 (5) 
 
 
 
 
 (27) 
 
 
 (10) 
 
 
 
 5 
 
 3f 
 
 20 
 
 
 L. 
 
 
 
 
 
 
 (29) 
 
 
 (12) 
 
 
 
 10 
 
 13 
 
 
 Gum benzoin, 
 
 R. 
 
 I/. 
 
 
 
 7 
 8 
 
 7 
 7 
 
 
 
 (19) 
 (17) 
 
 
 
 
 
 (6) 
 (8) 
 
 
 10 
 
 Gum ammoniac 
 
 (i)R. 
 
 
 
 
 
 (7) 
 
 
 
 
 (9) 
 
 (8) 
 
 
 (12) 
 
 
 
 & gutta-percha: 
 
 (I) I.. 
 
 
 
 
 
 (17) 
 
 
 
 
 (8) 
 
 (10) 
 
 
 (21) 
 
 
 
 (I) First 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Utrecht cylinder. 
 
 (2)R. 
 
 
 
 
 
 
 
 
 
 (9) 
 
 
 
 
 
 
 (2) Second 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Utrecht cylinder, 
 
 (2)L. 
 
 
 
 
 
 
 
 
 
 (8) 
 
 
 
 
 
 
 (3) Home-made 
 
 (3)R. 
 
 
 
 
 
 
 
 
 9 
 
 2 
 
 
 
 
 
 
 cylinder. 
 
 (3)Iv. 
 
 
 
 
 
 
 
 
 18 
 
 4 
 
 
 
 
 
 
 Yellow wax, 
 
 R. 
 
 I/. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 2-5 
 
 Cocoa-butter, 
 
 R. 
 
 10 
 8 
 
 (16) 
 (17) 
 
 
 
 
 a! 
 
 
 7 
 12 
 
 
 
 
 
 
 1 
 
 Tolu balsam, 
 
 R. 
 
 14 
 19 
 
 
 
 
 4 
 3 
 
 I 
 I 
 
 
 (62) 
 (49) 
 
 
 
 I 
 6 
 
 
 9 
 
 s 
 
 I 
 
 Musk-root, 
 
 R. 
 
 
 
 
 
 
 
 4 
 8 
 
 
 
 
 7 
 5 
 
 
 
 
 Mutton-tallow, 
 
 R. 
 
 
 
 
 
 
 
 4 
 6 
 
 
 
 
 2 
 5 
 
 
 
 
 Asafcetida, 
 
 R. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Oil of Mace. 
 
 R. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 I/. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Coumarine, 
 
 R. 
 
 17 
 
 S'-X 
 
 (20) 
 
 (6) 
 
 (8) 
 
 (I) 
 
 
 (25) 
 
 (12) 
 
 (12) 
 
 S! 
 
 (27) 
 
 ^36) 
 ^33) 
 
 
 
 I/. 
 
 23 
 
 (2) 
 
 
 (6) 
 
 (12) 
 
 (3) 
 
 
 (21) 
 
 (11) 
 
 (10) 
 
 (54) 
 
 
 Glycerine soap. 
 
 R. 
 
 I.. 
 
 
 
 
 
 
 (19) 
 (15) 
 
 
 (12) 
 (13) 
 
 (7) 
 (4> 
 
 
 
 
 
 2 
 
 Heliotropine, 
 
 R. 
 
 24 
 
 
 
 
 
 
 (33) 
 
 
 
 
 
 
 (9) . 
 
 
 Musk. 
 
 L. 
 R. 
 
 39 
 
 
 
 
 (8) 
 
 
 (33) 
 
 
 
 
 (7) 
 
 
 ;io) 
 
 
 
 L. 1 
 
 1 
 
 (2)1 
 
 
 
 
 
 
 (7) 
 
 1 
 
 
WEBER S I,AW TO SMELL. 
 
 43 
 
 Tabi;B I. — Continued. 
 
 Part 2. Stimulus-Limina Arranged to Show Variations Due to 
 Practice and to Differences of Temperature. 
 
 SUBJECT. 
 
 SUBSTANCE. 
 
 NOSTRII,. 
 
 Value of r A, in ^m. 
 
 THERMOMETER 
 READING. 
 
 Be. 
 
 Tolu balsam 
 
 R. 
 Iv. 
 
 (32) 
 (35) 
 
 S3°F 
 
 
 
 R. 
 
 14 
 
 60 
 
 
 
 L. 
 
 19 
 
 
 K. 
 
 
 R. 
 
 Iv. 
 
 (24) 
 (28) 
 
 54 
 
 
 
 R. 
 
 (21) 
 
 52 
 
 
 
 L. 
 
 (22) 
 
 
 
 
 R. 
 
 4 
 
 64 
 
 
 
 L. 
 
 3 
 
 
 
 Rosewood 
 
 R. 
 L. 
 
 (i5) 
 (29) 
 
 59 
 
 
 
 R. 
 
 (13) 
 
 64 
 
 
 
 L. 
 
 (22) 
 
 
 
 
 R. 
 
 6 
 
 62 
 
 
 
 L. 
 
 8 
 
 
 P. 
 
 Cocoa butter 
 
 R. 
 
 (27) 
 (26) 
 
 62 
 
 
 
 R. 
 
 (19) 
 
 62 
 
 
 
 L. 
 
 (27) 
 
 
 
 
 R. 
 
 7 
 
 66 
 
 
 
 L. 
 
 12 
 
 ( 
 
 All the values of rX given in this Table are averages of several de- 
 terminations taken on the same day. Those enclosed in parentheses 
 ■were found when the subjects had had little or no experience with the 
 substances in question. Those not so enclosed were found after the 
 respective substances had been used by the several subjects m differ- 
 ence determinations. In the first part of the Table, the limen given 
 is in every case the last limen found for the subject and substance, 
 and all the last limina found are given. The second part of the Table 
 simply contains results selected by way of illustration, but all tne 
 limina found for the subject with the substance in question are 
 included. . , 
 
 In Part i, all the substances but the last four are taken in order 
 from a Table in which Zwaardemaker arranges various materials for 
 solid odorous cylinders in the order of their intensity. ^ The limma 
 in the column headed Z are those given by him in another Table as 
 normal at a temperature of 15° C, or 59° F-' The temperatures at 
 which our records were taken lay for the most part between 60 ana 
 70" F. Our limina ought, therefore, to be lower than his, insteaa 01 
 higher. We cannot satisfactorily explain the difference between our 
 results and his in the matter of stimulus-limina. That the limma of 
 Americans should be higher than those of Dutchmen is not indeed 
 surprising, but the entire change in the rank of the substances is. 
 AccordinI to Dr. Renter, as cited by Zwaardemaker, the gum ammo- 
 niac and gutta-perc ha cylinder is forty times as strong as the vulcan- 
 
 1 Op. cit., p. 118. 
 2P. 167. 
 
44 GAMBiiB : 
 
 ized rubber, and the musk-root is five times stronger than the former. 
 The tallow, Zwaardemaker says, is stronger still. We regret that we 
 could not find stimulus-limina oftener. The washing of the tube 
 consumed so much time that this was impossible. We feel that the 
 results embodied in Table I are the most unsatisfactory part of our 
 work. Yet if allowances be made for exhaustion in some of the 
 results of C. and Sh., and for expectation gradually controlled by 
 practice in the cases of Bi., M. and Rog., the Table will serve its 
 purpose.^ 
 
 We have not space to give our temperature records in full. They 
 varied so irregularly that the arithmetical mean by no means repre- 
 sents the most common reading. As the steam had to be kept shut 
 off when we were not in the laboratory, the exact regulation of the 
 temperature involved serious practical difficulties, and for most of our 
 work it was a matter of minor importance, for in difference-determi- 
 nations variations of temperature and moisture affect the standard- 
 stimulus and the stimulus of comparison equally, and may, therefore, 
 be disregarded. Indeed, our barometer-records, though carefully 
 kept, proved to be wholly a work of supererogation, for in the case of 
 the very few substances (glycerine soap, coumarine, heliotropine, 
 vanillin'e, and allyl sulphide) which were somewhat soluble in water 
 and yet not in aqueous solution, we did not succeed in finding stimu- 
 lus-limina on different days.'' Practice lowered the stimulus-limina 
 in a conspicuous manner, but the effect of variations in temperature 
 can 'only occasionally be traced in the complete results. Part 2 of 
 Table I illustrates this fact with fairness. 
 
 It only remains to say that Be., C.,K., N., Se. and T. worked twice 
 a week for at least part of the year and the others once. 
 
 Section 2. Results Obtained by the Method of Just 
 Noticectble Differences. 
 Since in the nature of the case numerical proof of the applica- 
 bility of Weber's law to a given sense department cannot be 
 thrown into the form of averages, and since we have not 
 space for the great mass of figures which we have at hand, 
 we must ofEer first samples and then summaries of our evi- 
 dence, and content ourselves with them. Tables II and 
 III are the samples, and Tables IV, V and VI are summa- 
 ries from different points of view. Tablel V constitutes the 
 most decisive proof of the validity of the law. Tables V and 
 VI are intended to confirm the conclusion to be drawn from 
 Table IV, and to show the probable value of A n In Tables 
 
 r 
 III, IV, V and VI, every value given or enumerated is an av- 
 erage of the results "of one day's work with one subject, nostril, 
 substance and standard. All the work done with this method, 
 however unsatisfactory, is represented in Tables V and VI. 
 
 ^ The writer's own limina are lower than those of any of the subjects. 
 Abnormal keenness of smell has persisted from childhood, in spite of 
 the usual share of "colds." 
 
 ^ For the effect of atmospheric moisture in Zwaardemaker's method, 
 see Chapter I, Section 2. 
 
wbber's i,aw to smeli,. 
 
 45 
 
 Tabi,b II. CoNSBCuTivB RbsuI/TS op One Subject, T. 
 
 Date. 
 
 Substance. 
 
 sostm, 
 
 No. of 
 values 
 aver- 
 aged. 
 
 r 
 
 i\ro 
 
 Aru 
 
 Ar 
 
 r 
 
 Disturbing 
 factors. 
 
 Nov. 9, 
 
 Tolu 
 
 R. 
 
 6 
 
 20 
 
 4(2) 
 
 7(3) 
 
 hVz 
 
 4 
 
 
 
 balsam 
 
 L. 
 
 
 
 5(2) 
 
 5(1) 
 
 5 
 
 4 
 
 
 13. 
 
 
 R. 
 
 6 
 
 30 
 
 2(1) 
 
 14(2) 
 
 8 
 
 4 
 
 
 
 
 L. 
 
 
 
 3(2) 
 
 9(5) 
 
 6 
 
 
 
 16, 
 
 
 R. 
 
 3.4 
 
 20 
 
 1(1) 
 
 6(4) 
 
 3>^ 
 
 6[Z] 
 
 
 
 
 L. 
 
 3-3 
 
 
 4(2) 
 
 4(2) 
 
 4 
 
 5[Z] 
 
 
 
 
 R. 
 
 4 
 
 30 
 
 6(3) 
 
 8(2) 
 
 7 
 
 4 
 
 
 
 
 L. 
 
 
 
 4(2) 
 
 7(4) 
 
 5>^ 
 
 5 
 
 
 19. 
 
 
 R. 
 
 4,3 
 
 20 
 
 4(1) 
 
 1(2) 
 
 2>^ 
 
 Z [Z] 
 
 
 
 
 L. 
 
 3,3 
 
 
 5(3) 
 
 6(4) 
 
 5^ 
 
 4[Z] 
 
 
 
 
 R. 
 
 4 
 
 30 
 
 6(2) 
 
 7(3) 
 
 (>% 
 
 5 
 
 
 
 
 L. 
 
 
 
 4(4) 
 7(2) 
 
 5(3) 
 
 A% 
 
 Z 
 
 
 30- 
 
 Russian 
 
 R. 
 
 4,2 
 
 24 
 
 3(1) 
 
 5 
 
 5[Z] 
 
 
 
 leather, 
 
 L. 
 
 
 
 6(1) 
 
 5(2) 
 
 SK 
 
 4 
 
 
 
 
 R. 
 
 4 
 
 44 
 
 8(2) 
 
 9(2) 
 
 ^'A 
 
 5 
 
 
 
 
 ly. 
 
 
 
 10(3) 
 
 12(3) 
 
 II 
 
 4 
 
 
 Dec. 10, 
 
 
 R. 
 
 4 
 
 24 
 
 3(2) 
 
 6(2) 
 
 Ayi 
 
 5 
 
 
 
 
 L. 
 
 
 
 6(4) 
 
 7(2) 
 
 (>A 
 
 4 
 
 
 
 
 R. 
 
 4 
 
 44 
 
 6(4) 
 
 10(3) 
 
 8 
 
 6 
 
 
 
 
 L. 
 
 
 
 8(3) 
 
 11(4) 
 
 9>^ 
 
 5 
 
 
 14. 
 
 Asafoetida, 
 
 R. 
 
 3 
 
 8 
 
 5(4) 
 
 4(1) 
 
 4>^ 
 
 A 
 
 
 
 
 L. 
 
 
 
 6(0) 
 
 7(1) 
 
 eyi 
 
 A 
 
 
 
 
 R. 
 
 3 
 
 13 
 
 4(3) 
 
 10(2) 
 
 7 
 
 A 
 
 
 
 
 L. 
 
 2.3 
 
 
 5(1) 
 
 8(1) 
 
 eyi 
 
 2 [2] 
 
 
 
 Russian 
 
 R. 
 
 2 
 
 9 
 
 5(3) 
 
 
 
 -[Z] 
 
 Exhaustion. 
 
 
 leather, 
 
 Iv. 
 
 3.1 
 
 
 4(2) 
 
 o(-) 
 
 2 
 
 5 [6] 
 
 
 16, 
 
 Asafoetida, 
 
 R. 
 
 2,1 
 
 8 
 
 3(3) 
 
 6(-) 
 
 4>^ 
 
 A[Z] 
 
 General 
 fatigue. 
 Exhaustion. 
 
 
 
 L. 
 
 3.1 
 
 
 4(1) 
 
 3(-) 
 
 3>^ 
 
 2 [5] 
 
 
 
 R. 
 
 3 
 
 13 
 
 3(2) 
 
 6(2) 
 
 4>^ 
 
 3 
 
 
 
 
 -u. 
 
 2.3 
 
 
 8(1) 
 
 5(2) 
 
 sy. 
 
 2 [3] 
 
 
 
 Russian 
 
 R. 
 
 3.2 
 
 9 
 
 6(4) 
 
 1(1) 
 
 i'A 
 
 3 [3] 
 
 
 
 leather. 
 
 L. 
 
 3.1 
 
 
 5(1) 
 
 3(-) 
 
 4 
 
 2 [6] 
 
 
 20. 
 
 Asafoetida, 
 
 R. 
 
 1.3 
 
 8 
 
 3(-) 
 
 3(2) 
 
 3 
 
 3[Z] 
 
 Exhaustion. 
 
 
 
 Iv. 
 
 I, I 
 
 
 3(-) 
 
 o(-) 
 
 ^A 
 
 5 [-] 
 
 
 
 
 R. 
 
 3.2 
 
 13 
 
 6(1) 
 
 6(1) 
 
 6 
 
 2 [3] 
 
 
 
 
 L. 
 
 3.2 
 
 
 7(0 
 
 3(2) 
 
 5 , 
 
 3 [3] 
 
 
 
 Russian 
 
 R. 
 
 1.2 
 
 9 
 
 lo(-) 
 
 1(2) 
 
 s'A 
 
 A [6] 
 
 Exhaustion. 
 
 
 leather. 
 
 L. 
 
 3.1 
 
 
 3(1) 
 
 i(-) 
 
 2 
 
 5[Z] 
 
 
 Jan. 8, 
 
 Cedar, 
 
 L. 
 
 4 
 
 22 
 
 8(2) 
 
 8(3) 
 
 8 
 
 3 
 
 Exhaustion. 
 
 II, 
 
 
 R. 
 
 4.2 
 
 22 
 
 8(2) 
 
 6(2) 
 
 7 
 
 3 [5] 
 
 ( Exhaustion. ) 
 1 Pungency. ) 
 
 
 
 L. 
 
 3.4 
 
 
 6(3 
 
 8(3) 
 
 7 , 
 
 3 [4] 
 
 
 
 I.. 
 
 
 42 
 
 ii(i) 
 
 10(1) 
 
 io>^ 
 
 4 
 
 
 22. 
 
 Asafoetida, 
 
 R. 
 
 2 
 
 12 
 
 8(4) 
 
 8(0) 
 
 8 
 
 A 
 
 General fatigue. 
 
 
 
 L. 
 
 
 
 5(3) 
 
 8(1) 
 
 6/2 
 
 A 
 
 
 
 
 R. 
 
 2 
 
 22 
 
 14(2) 
 
 13(2) 
 
 ^3/2 
 
 A 
 
 
 
 
 L. 
 
 
 
 8(1) 
 
 14(0) 
 
 II 
 
 2 
 
 
 Feb. I, 
 
 
 R. 
 
 3 
 
 22 
 
 8(2) 
 
 8(1) 
 
 8 
 
 3 
 
 
 
 
 Iv. 
 
 
 
 8(3) 
 
 8(3) 
 
 8 
 
 3 
 
 
 
 
 R. 
 
 3 
 
 12 
 
 10(1) 
 
 8(1) 
 
 9 
 
 A 
 
 
 
 
 Iv. 
 
 
 
 9(2) 
 
 7(1) 
 
 8 
 
 A 
 
 
 5' 
 
 Coumarine, 
 
 R. 
 
 3 
 
 56 
 
 14(2) 
 
 7(4) 
 
 io>^ 
 
 5 
 
 
 12, 
 
 Heliotropine, 
 
 R. 
 
 4 
 
 28 
 
 15(2) 
 
 11(0) 
 
 13 
 
 2 
 
 
46 
 
 GAMBLE : 
 
 
 
 Tabi<e II.— 
 
 Continued. 
 
 
 
 
 DATS. 
 
 Substance. 
 
 nostril, 
 
 No. of 
 values 
 aver- 
 
 r 
 
 Aro Aru 
 
 Af 
 
 Ar 
 
 Disturbing 
 factors. 
 
 
 
 
 aged. 
 
 
 
 
 
 V 
 
 
 Feb. 12, 
 
 Heliotropine, 
 
 L. 
 
 
 
 13(1) 
 
 11(2) 
 
 12 
 
 2 
 
 
 
 
 R. 
 
 3 
 
 48 
 
 18(0) 
 
 17(1) 
 
 ny^ 
 
 3 
 
 
 
 
 Iv. 
 
 
 
 20(2) 
 
 15(1) 
 
 11% 
 
 3 
 
 
 i8, 
 
 
 R. 
 
 2 
 
 28 
 
 17(0) 
 
 13(0) 
 
 15 
 
 A 
 
 
 
 
 L. 
 
 
 
 14(2) 
 
 11(0) 
 
 I2>^ 
 
 2 
 
 
 
 
 R. 
 
 2 
 
 48 
 
 18(1) 
 
 15(0) 
 
 i6>^ 
 
 3 
 
 
 
 
 Iv. 
 
 
 
 19(5) 
 
 14(0) 
 
 16% 
 
 3 
 
 
 26. 
 
 
 R. 
 
 2 
 
 27 
 
 13(0) 
 
 10(0) 
 
 ItVz 
 
 2 
 
 
 
 
 Iv. 
 
 
 
 12(1; 
 
 8(1) 
 
 10 
 
 3 
 
 
 
 
 R. 
 
 2 
 
 47 
 
 19(1) 
 
 14(3) 
 
 i6>4 
 
 3 
 
 
 
 
 Iv. 
 
 1,2 
 
 
 i6(-) 
 
 9f2) 
 
 12>^ 
 
 4 
 
 
 Mar. I, 
 
 
 R. 
 
 3 
 
 27 
 
 13(1) 
 
 8(0) 
 
 ioy2 
 
 3 
 
 General fatigue. 
 
 
 
 Iv. 
 
 
 
 12(2) 
 
 8(0) 
 
 10 
 
 3 
 
 
 
 
 R. 
 
 3 
 
 47 
 
 18(1) 
 
 15(0) 
 
 16^ 
 
 3 
 
 
 
 
 Iv. 
 
 
 
 18(0) 
 
 15(1) 
 
 16% 
 
 3 
 
 
 3. 
 
 Valerianic 
 
 R. 
 
 3 
 
 18 
 
 15(2) 
 
 9(1) 
 
 12 
 
 A 
 
 ( Pungency. ) 
 j Exhaustion. ) 
 
 
 acid, 
 
 L. 
 
 
 
 14(2) 
 18(1) 
 
 7(3) 
 
 I0>^ 
 
 A 
 
 
 
 R. 
 
 21 
 
 38 
 
 13(1 
 
 15>^ 
 
 3 
 
 
 
 
 L. 
 
 2,3 
 
 
 16(2) 
 
 9(2) 
 
 12;^ 
 
 3 
 
 
 8, 
 
 
 R. 
 
 2 
 
 18 
 
 13(1) 
 
 3(2) 
 
 8 
 
 2 
 
 
 
 
 Iv. 
 
 3 
 
 
 12(1) 
 
 4(2) 
 
 8 
 
 2 
 
 
 
 
 R. 
 
 2 
 
 38 
 
 16(2) 
 
 6(4) 
 
 11 
 
 4 
 
 
 
 
 L. 
 
 1,2 
 
 
 i8(-) 
 
 5(0) 
 
 ii>^ 
 
 3 
 
 
 18, 
 
 
 R.- 
 
 2,1 
 2 
 
 18 
 
 15(2) 
 15 3 
 
 4(-) 
 3(2) 
 
 9% 
 
 9 , 
 
 A 
 2 
 
 'General fa- 
 tigue. Nose- 
 bleed during 
 
 
 
 R. 
 
 2,1 
 
 38 
 
 24(2) 
 
 ii(-) 
 
 ^7'A 
 
 2 
 
 .the day. 
 
 
 
 I.. 
 
 2 
 
 
 20(1) 
 
 11(0) 
 
 5(1) 
 
 ts'A 
 
 3 
 
 
 19, 
 
 
 R. 
 
 2,3 
 
 18 
 
 11(1) 
 12(0') 
 
 8 
 
 2 
 
 f Irritation of "1 
 J nasal mem- 1 
 
 
 
 L. 
 
 2 
 
 
 — 
 
 
 
 — 
 
 1 branes. ( 
 
 
 
 R. 
 
 3,2 
 
 38 
 
 16(1) 
 17(1) 
 
 10(4) 
 
 13 
 
 3 
 
 [Exhaustion. J 
 
 
 
 Iv. 
 
 2 
 
 
 10(3) 
 
 i3>^ 
 
 3 
 
 
 21, 
 
 
 R. 
 L. 
 
 3 
 3.2 
 
 18 
 
 13(1) 
 13(0) 
 
 7(2) 
 
 10 
 10 
 
 A 
 A 
 
 Irritation of ' 
 nasal mem- 
 - branes. 
 
 
 
 R. 
 
 3 
 
 38 
 
 16(1) 
 
 i4>^ 
 
 3 
 
 Smell of 1 
 
 26. 
 
 Citral, 
 
 R. 
 
 2 
 2 
 
 13 
 
 18(1) 
 8(1) 
 
 "S 
 
 14>^ 
 6% 
 
 3 
 
 2 
 
 .tobacco. J 
 Irritation of 
 nasal mem- 
 
 
 
 Iv. 
 
 3.2 
 
 
 8(1) 
 
 4(2) 
 
 6 
 
 2 
 
 branes. 
 
 Apr. 16, 
 
 
 R. 
 
 Iv. 
 R. 
 
 2,1 
 3.2 
 1.2 
 
 28 
 13 
 
 13(0) 
 12(2) 
 
 7(-) 
 
 ^ 
 
 0(0) 
 2(1) 
 
 10% 
 9% 
 
 yA 
 
 3 
 3 
 4 
 
 Homatropin 
 freshly put 
 .into the eyes. 
 
 
 
 t. 
 
 2 
 
 
 8(1) 
 
 
 3 
 
 
 
 
 a. 
 
 3 
 
 28 
 
 12(0) 
 
 12(1) 
 
 4(2) 
 
 8 
 
 4 
 
 
 
 
 L. 
 
 2,3 
 
 
 5(2) 
 
 8H 
 
 3 
 
 
 T. whose results seem best fitted to be used as an illustratiouiworked 
 twice a week, as a rule, during the time covered by this Table. No 
 difference-determinations obtained from her during this time by the 
 method of just noticeable differences have been omitted. In October, 
 we worked with her once a week, but were occupied chiefly in finding 
 stimulus-limina. She also worked for us several hours late in the 
 spring with results which did not differ materially from those em- 
 bodied in the table. The fourth column of the Table gives the number 
 of values averaged to obtain the figures given in the columns headed 
 
wbber's law to smell. 47 
 
 hro and Ar». If two figures stand on a line in the fourth column, the 
 first refers to /\ro and the second to i\ru. One figurerefers not to both 
 together but to each alike. The numbers in parentheses are all mean 
 variations. A dash in parentheses means that the number by which 
 it stands is not an average. In the column headed i\r, for the sake 
 
 r 
 of brevity values greater than % are indicated by the letter A ; values 
 equal to Yz or lesSj but nearer to yi than to yi, are indicated by the 
 figure a ; values equal to y^ or nearer to Y^ than to ^ or to X. by the 
 figure 3 ; values equal to X or nearer to X than to Yi <" to \, by the 
 figure 4 ; values equal to \ or nearer to \ than to % or to \, by the fig- 
 ure 5 ; values equal to J or greater, but nearer to \ than to \, by the 
 figure 6 ; and values less than \, by the letter Z. Every subject 
 sometimes moved the cylinder beyond the standard, and the readmg, 
 if taken at all, could be written only as a minus (quantity. This cross- 
 ing of the standard almost never occurred with the fluid-mantle 
 olfactometer, and when it did the error was so easily explained that 
 the reading was not taken. Between November 9 and the time when 
 the liquids were first used, two sets of averages were obtained, the 
 first by excluding and the second by including these negative quanti- 
 ties when they occurred. In Tables IV, V and VI, only values 
 representing no negative quantities and differing from averages of 
 the same series with the addition of such quantities by less than % 
 are included in the enumeration. The averages enclosed in square 
 brackets in Table II were found by including minus quantities in the 
 average values of l\ro and J\ru. From all unbracketed averages, nega- 
 tive quantities are excluded. A dash in square brackets indicates 
 that the corresponding value of l\r is itself a negative quantity. 
 
 The efEect of some of the disturbing factors which are con- 
 stant can best be illustrated in connection with this Table. 
 Besides exhaustion, adhesion, and the tendency to judge in 
 terms of hand-movement, which we call for short "the move- 
 ment-error," some obstruction of the nasal passages, some 
 slight compensating-smells, such as that of the absorbent 
 cotton used to wipe the inhaling-tube, and some distraction of 
 the attention in manipulating the large instrument, must be 
 taken for granted with all the subjects. Only marked ex- 
 haustion is expressly noted in Table II. Another source of 
 error which comes into operation with asafcetida, oil of mace, 
 Russian leather, and all the liquids except coumarine, helio- 
 tropine and musk is the escape of odor between the cylinder 
 and the tube. The effect of this circumstance, which was 
 mentioned in Section 2 of Chapter 2, must be to make the 
 value of A r too large, because it makes the standard larger 
 
 r 
 
 than the instrument indicates. If, for example, r on the in- 
 strument is 20 mm. , but really is 25 mm. , and A r is found to be 
 5 mm., then _Ar will be nominally % while really it is \. 
 
 r 
 As we explained in discussing the disadvantages of the 
 method of just noticeable differences, the effect of the move- 
 ment-error is to make the value of A r smaller for the larger 
 
48 GAMBLE : 
 
 standards, and thus to conceal the operation of Weber's law. 
 If we look now at the values o f A r in Table II, we shall see at 
 
 r 
 a glance that this variation exists. It should be noted that 
 no variation in the order of the standards will eliminate the 
 movement-error. If the smaller standard is given first and a 
 certain habit of movement acquired, this habit will make A r 
 
 r 
 for the larger standard too small. If the habit is acquired in 
 connection with the larger standard, it will make A r for the 
 
 r 
 smaller too large. It is true that if the standards were alter- 
 nated by single determinations, rather than by short series, a 
 habit of movement would be less likely to establish itself, but 
 such a procedure is excessively confusing to the subject in the 
 case of smell, and, moreover, all work done with the smaller 
 standard after the organ is blunted with the larger is more or 
 less unsatisfactory. If the distance between the standards 
 and the stimuli offered as decidedly greater or less were kept 
 not absolutely but relatively equal, the movement-error would 
 be concealed. The fact that these distances cannot be kept 
 absolutely equal,, if the stimulus of comparison is to be accepted 
 as such by the subject, is in itself no small confirmation of 
 Weber's law. As a matter of fact, they were kept as nearly 
 equal as possible, both to avoid concealing the movement-error 
 and to minimize exhaustion by strong stimuli. They often 
 varied in the same series as the subject's organ became blunted 
 to all differences and then recovered itself, but in general for a 
 standard of lo or 15 mm., the difference was made 10 mm. ; 
 for a standard of 20 or 30, 15 ; for a standard of 40 or 50, 20, 
 and for a standard of 60 or 70, 25. 
 
 The moving back and forth at the limen is some safe- 
 guard against the error, yet the tendency o f A> to be smaller 
 
 r 
 for the larger standards is apparent in the results of subjects 
 whose attention was good and whose movements were careful. 
 Thus, it is particularly well-marked in the work of Se., who 
 was certainly not inferior to any of our subjects. Moreover, the 
 same tendency showed itself when the different standards were 
 used on different days, and a habit in such nice adjustments 
 could scarcely persist from day to day or week to week with so 
 little practice. If (1) the movement-error is one explanation 
 of the variation, (2) the escape of odorous vapor is in some 
 cases another. The equal though unmeasured increment is 
 a larger fraction of the smaller standard than of the larger. 
 If our standards are 20 and 40 and the increment is 4, while 
 
WEBER'S LAW TO SMELI,. 49 
 
 Ar~ ^ in both cases, then A r will be 6 in one case and 1 1 
 r 
 in the other, and we must write the values of A r f^ and ff. 
 
 r 
 We believe that (3) a fortuitous circumstance in connection 
 with the standard olfactometer is another factor in the same 
 result. Usually, the last movement made by the subject is an 
 outward movement. He moves from a point decidedly differ- 
 ent from the standard to subjective equality, and then a little 
 way back again, — in and out once or oftener. In moving the 
 cylinder the hand is apt to slip, and the accidental increment to 
 A y is a larger fraction of the smaller standard than of the larger. 
 Adhesion is not a factor in the case, for it is larger for the 
 larger standard, varies with the length of the determination, 
 has an opposite effect upon A ro and A ru, and is balanced in 
 an indefiilite way by exhaustion. 
 
 It should be noted in Table II that at first t^ru is usually slightly 
 larger than is.ro, but that with practice this variation is reversed. The 
 natural effect of exhaustion is to make i\ro larger than ISru, for ex- 
 haustion does not affect the standard stimulus and stimulus of com- 
 parison equally, but progresses all the time that the latter is manipu- 
 lated. This tendency is in a manner checked by the time-error and 
 by adhesion. (See Chapter I, Section 4.) Now Be., the one subject 
 who had had some experience in smell-experiments laefore the begin- 
 ning of this course, tended from the first to make i\ro greater than iSru. 
 All the other subjects at first made i\ru greater than /\ro, but all ex- 
 cept Hog., Se. and Sh. changed the tendency with practice or began 
 to do so. Rob., N. and T. altered it very soon and decidedly. With 
 Se. the values were usually almost equal. This alteration with prac- 
 tice seems to show that exhaustion causes more disturbance than ad- 
 hesion and the time-error put together. This is what we should 
 expect, for although the subject rested while the tube was being 
 cleaned, yet the removal of adhesion was absolute, while the recupera- 
 tion of the organ was less complete each time.^ We never can be 
 quite sure, however, whether exhaustion is really decreasing the 
 strength of stimuli regularly, or is blunting all differences or making 
 all movements haphazard. When a subject complained that his nose 
 felt "hot," "dry," "rough," "scrapy," "sore," or "numb," his 
 movements were often erratic, and the smaller stimulus sometimes 
 seemed as strong as the larger, which probably stunned the already 
 weary organ instantly. The dryness, no doubt, was due to the vigor- 
 ous breathing. The tongue of a fever-patient will become much more 
 parched and black if respiration through the nose is obstructed. 
 
 The original tendency to make hro decidedly smaller than Arw, and 
 the difficulty of finding the lower stimulus-limen are probably due to 
 the same cause. Both cumulative stimulation and memory after- 
 images might produce the tendency, though both would be counter- 
 acted in a measure by the moving to and frd at the limen. Against 
 both the subject would learn to guard in a measure. Be. mentioned 
 " after-images " of cocoa-butter, and Se. of tolu balsam. Frequently 
 a subject would complain that he could not "get the strong smell out 
 of his nose." 
 
 1 Zwaardemaker : op. cit., pp. 203-204. 
 4 
 
so 
 
 GAMBLE : 
 
 In the mean variations, as a whole, it is impossible to trace any 
 tendency to be larger in judgments made with reference to the larger 
 standard. Though the larger standard was usually given last, the 
 effect of exhaustion in producing erratic judgments towards the end 
 of the hour seems to have been balanced by a certain lack of practice. 
 At the beginning of the hour, there is a sort of conscious awkwardness, 
 characteristic of these smell-judgments when first attempted. It is 
 impossible to draw from our figures any conclusion in regard to the 
 delicacy of quantitative sensible discrimination in smell. The varia- 
 tions were evidently controlled to a great extent by the peculiari- 
 ties of the instrument and the subject's habit of movement, and 
 it must be confessed that from day to day the effect of practice 
 upon them was not very clearly marked. All the subjects had 
 smaller mean variations when using the fluid-mantle olfactometer, 
 but this fact can hardly have been due to practice, for, although the 
 other instrument was used first in every case, Rob., Rog. and T. re- 
 turned to it after using the large instrument for a while, and showed 
 the same mean variations as they did at the beginning. Moreover, 
 the diflficulty of turning the screw-head of the large instrument and 
 
 Table III. 
 Complete Results for One Solid and One Liquid Substance. 
 
 SUBSTANCE. 
 
 SUBJECT. 
 
 VAI,UES OF 
 
 Ar 
 
 17 17 22 19 14 „, 17 r,-n(\ 3 5 
 ffT) ■ST. T¥. TT> ■?¥ W. TX ^"^ Tr5 
 
 /f w. fi and tW 
 
 8 1,7 22 18 -mr 19 
 ■gr W. 7"^, -j-g- W. T-g- 
 
 1 4 „- 18 1 5 T,, 19 1 5 -nr 13 
 
 16 14 
 
 T!r> FT 
 
 12 „, 17 12 „, 17 16t,t24 12™^ 28 
 
 X^ W. Tj-, -j^ W. 7-if, ^2" ^- TJ> TT "'■ 7T 
 
 24 17 25 28-nT 25 25 22 „, 29 
 
 19 -nr 27 17 -nr 27 
 TS W- ¥T> T'% W. -^ 
 
 1 4 „; ) 8 1 5 „, 19 
 ■gT ^- TTi ■ST W. 7-2" 
 
 Gray 
 rubber, 
 
 Coumarine, 
 
 Be. 
 
 D. 
 
 Se. 
 
 Be. 
 
 Bi. 
 
 C. 
 
 D. 
 K. 
 M. 
 
 N. 
 
 P. 
 Rob. 
 
 Rog. 
 
 Se. 
 Sli. 
 T. 
 
 -Mr 
 
 14 w 
 
 20 
 ■^T 
 
 26 w 
 
 2 4 T,, 2 6 21 -1,7 _2 6_ 
 
 T 88 27 -nr 83 19—, 21 16 ™- 18 
 
 14 „, 25 18„, 26 
 ■ST W. T^, TJ W. T-j- 
 
 20 18 xt, 21 20 -[,7 22 19. „, 28 
 ■nr 2 3 17 TI7 2 8 2 1 -r,, 2 6 26 ^j, 26 
 !7 Ilw28 1-l-wi4 
 
 11 
 ■JT 
 
 18 
 
 TT) 
 
 21 
 
 TTT 
 
 ■w. 
 
 27 
 
WEBER'S I.AW TO SMEI,!,. 
 
 51 
 
 the propensity of the movable cylinder of the small instrument for 
 slipping are quite enough to explain the fact. The mean variations 
 of Rob., Rog., Se. and Sh. closely resembled those of T., both in size 
 and in degree of uniformity. Those of Be., Bi., C, M. and N. ran 
 higher, and were more irregular. This fact was undoubtedly due to 
 hasty movements in the cases of Bi., C. and M., and to exhaustion in 
 the cases of Be. and N. D.'s mean variations were large and irregu- 
 lar in the beginning, but improved with his manner of moving the 
 cylinder, and ^.'s also were large at first, but finally approximated to 
 ■ T.'s. P.'s were suspiciously small, as small with the fluid-mantle as 
 with the standard olfactometer, and indicated the movement-error 
 beyond a doubt. 
 
 Results connected by W. ( " with " )y,were found on the same day 
 for the saine nostril. The values obtained with gray rubber were 
 chosen for illustration because vulcanized rubber was used with three 
 different methods, and those obtained with coumarine were taken 
 because this scent was used with all the thirteen subjects. Both sets 
 are fair samples of the whole mass of results. The series of Be. and D. 
 with gray rubber, and of Bi., C, K., M., N., Rob. and Sh. with cou- 
 marine, give pretty clear indications of the validity of Weber's law. 
 That of 5i?.with rubber, and those of D., P., Rog. and Sh. with couma- 
 rine, indicate the operation of the law simply by the fact that as a 
 rule the numerators of the fractions with the larger denominators are 
 larger. The series of Be. and T. with coumarine are too short to 
 prove anything by themselves. A series in which the numerators of the 
 fractions with the larger denominators are persistently smaller than 
 those of the fractions with the smaller denominators or equal to them 
 may be counted as tending to disprove the law. 
 
 In the complete set of results — counting the results of one subject 
 with one substance as one series — there are 55 series for solids. Out 
 of these, 15 indicate Weber's law clearly ; 14 indicate itfaintly ; 11 long 
 
 Tabi,e IV. 
 
 .Ar 
 
 Approximate Values of — obtained for Pairs of Standard Stimulus- 
 Intensities Sensed under the Same Conditions, — viz : 
 Subject, Nostril, Substance, and Hour. 
 
 hr 
 
 (I) 
 
 (*) 
 
 (2) 
 
 (2) 
 
 (I) 
 
 (I) 
 
 (2) 
 
 (2) 
 
 — 
 
 
 r^=2a 
 
 
 r^— 
 
 
 r=2a 
 
 
 
 
 r^—a 
 
 or2a-\- 
 
 r=a 
 
 a+{a 
 
 r=^a 
 
 or2a\- 
 
 r=a 
 
 a+{a 
 
 A. V. 
 
 C. 
 
 c. 
 
 C. 
 
 C. 
 
 C. 
 
 C. 
 
 C. 
 
 C. 
 
 >^(A) 
 
 20 
 
 3 
 
 14 
 
 II 
 
 10 
 
 
 7 
 
 I 
 
 %{2) 
 
 7 
 
 7 
 
 5 
 
 5 
 
 35 
 
 I 
 
 14 
 
 4 
 
 /3(3) 
 
 34 
 
 13 
 
 7 
 
 10 
 
 35 
 
 57 
 
 46 
 
 32 
 
 VaU) 
 
 9 
 
 32 
 
 21 
 
 7 
 
 6 
 
 34 
 
 17 
 
 32 
 
 \ (5) 
 
 3 
 
 II 
 
 9 
 
 12 
 
 3 
 
 3 
 
 3 . 
 
 12 
 
 % (6) 
 
 
 5 
 
 4 
 
 3 
 
 5 
 
 
 I 
 
 4 
 
 »€(Z) 
 
 I 
 
 3 
 
 I 
 
 13 
 
 I 
 
 
 2 
 
 5 
 
 Total, 
 
 74 
 
 74 
 
 61 
 
 61 
 
 95 
 
 95 
 
 90 
 
 90 
 
52 GAMBLE : 
 
 i <i 
 
 y% 
 
 yi Yi % \ 
 
 40 
 
 
 30 
 
 / A \ 
 
 „ \ 
 
 V y \ \ 
 
 40 
 
 30 
 
 .^^ 
 
 y% 'A H X i i 
 
 CuRVBS Ii,i,usTRATiNG THE Vai<ues OF Ar FOR SowDS WHEN r=a 
 
 r 
 AND 2 a OR 2 0+. (See Table IV. ) 
 
 series are of doubtful interpretation ; 13 series are too short to prove 
 anytliing ; and 2 tend to disprove the law. Out of 39 series for liquids, 
 24 indicate the law clearly, and 11 do so faintly, while 3 are too short 
 to count, and only i tends to disprove the law. 
 
 We may now proceed to the Tables which summarize the evidence. 
 
 As noted before. Table IV enumerates only values for standards 
 which can be paired as sensed under the same conditions. The left 
 column of each pair of columns enumerates values obtained for the 
 smaller standards in the pairs. The columns headed (1) enumerate 
 values for standards of which one was twice as strong as the other, 
 or more than twice as strong. The columns headed (2) enumerate 
 values for standards of which one was less than twice as strong 
 as the other. All values obtained for standards which can be paired 
 are included. A. V. stands for "Approximate Values," and C. for 
 "Cases." 
 
 We believe tliat we have accounted for the tendency of A r 
 
 r 
 to be somewhat smaller for the larger standards. In Table IV, 
 however, it is clear that the errors to which this tendency is 
 due do not serve to conceal the operation of Weber's law. If 
 certain absolute differences of smell-intensity were sensed and 
 Ar for a given standard were yi, then for a standard twice as 
 r 
 strong jt should be yi, not ^. 
 
 Tables V and VI are arranged to show such variations as 
 occur from subject to subject, and substance to substance. That 
 it may be seen that each subject used a variety of substances, 
 and that the different subjects used the substances in different 
 
60 
 
 WEBER'S LAW TO SMELL. 
 y* Vi % k 
 
 53 
 
 <i 
 
 60 
 
 Curves Illustratixg the Values of At for Liquids when r=a 
 
 r 
 AND 2 a OR 2 a+. (See Table IV.) 
 
 Of these curves, the heavy lines give the values for the smaller, 
 and the broken lines for the larger standards. The ordinates give the 
 number of cases, and the abscissae approximate values. 
 
 orders, we preface the Tables with the following list of sub- 
 stances as used in order by each subject : 
 
 Be. Black rubber, tolu, cocoa-butter, asafcetida, Russian 
 leather, gray rubber, coumarine, heliotropine, valerianic acid, 
 citral. 
 
 Bi. Cocoa-butter, coumarine, vanilline. 
 
 C. Gum benzoin, oil of mace, cedar, coumarine. 
 
 D. Gray rubber, gum benzoin, oil of mace, coumarine, oil 
 of camphor. 
 
 K. Tolu, rose-wood, asafcetida, Russian leather, gum am- 
 moniac and gutta-percha from Utrecht, oil of mace, coumarine, 
 musk, ethyl butyrate. 
 
 M. Cocoa-butter, coumarine. 
 
 N. Black rubber, tallow, musk-root, rose-wood, oil of 
 mace, heliotropine, oil of camphor, vanilline. 
 
54 
 
 GAMBLE : 
 
 P. Gum ammoniac and gutta-percha, home-made, glycer- 
 ine soap, oil of mace, coumarine, oil of camphor. 
 
 Rob. Glycerine soap, gum ammoniac and gutta-percha, 
 home-made, oil of mace, coumarine, vanilline, cedar, gum am- 
 moniac and gutta-percha from Utrecht. 
 
 Rog. Black rubber, paraffine, coumarine, oil of camphor, 
 car yophy nine, giun benzoin, oil of anise, laudanum. 
 
 Se. Tolu, rose-wood, tallow, asafcEtida, musk-root, gray 
 rubber, oil of mace, coumarine, musk, ethyl butyrate, citral, 
 caryophylline, allyl suphide. 
 
 Sh. Black rubber, cedar, gum ammoniac and gutta-percha, 
 from Utrecht, coumarine, oil of camphor. 
 
 T. Tolu, Russian leather, asafoetida, cedar, coumarine, 
 heliotropine, valerianic acid, citral, pyridin and yellow wax. 
 
 The fact that the order was not varied more extensively and 
 more systematically was due to practical difficulties with the 
 apparatus. 
 
 Tabi,e V. Approximate Vai,ues op — t Arranged to Show 
 
 
 Variations 
 
 FOR 
 
 iNDiviDUAi, Subjects. 
 
 
 
 Nature 
 
 Number of cases j ^PreSiSlt"^ i 
 
 Total 
 
 Subject. 
 
 of 
 stimuli 
 
 
 
 
 number 
 of cases. 
 
 ^}i(A) 
 
 5i(2) 
 
 %(S) 
 
 K(4) 
 
 4(5) 
 
 i(6) 
 
 <5(z) 
 
 Be. 
 
 S. 
 
 6 
 
 9 
 
 4 
 
 6 
 
 3 
 
 I 
 
 
 29 
 
 
 Iv. 
 
 5 
 
 5 
 
 16 
 
 5 
 
 5 
 
 I 
 
 I 
 
 38 
 
 Bi. 
 
 S. 
 
 
 
 
 4 
 
 4 
 
 I 
 
 3 
 
 12 
 
 
 L. 
 
 
 I 
 
 9 
 
 4 
 
 I 
 
 3 
 
 2 
 
 20 
 
 C. 
 
 S. 
 
 6 
 
 2 
 
 7 
 
 3 
 
 5 
 
 I 
 
 2 
 
 26 
 
 
 L. 
 
 
 3 
 
 6 
 
 3 
 
 
 
 
 12 
 
 D. 
 
 S. 
 
 9 
 
 4 
 
 3 
 
 6 
 
 I 
 
 
 
 23 
 
 
 L. 
 
 
 7 
 
 6 
 
 3 
 
 
 
 
 l6 
 
 K. 
 
 S. 
 
 3 
 
 6 
 
 13 
 
 5 
 
 I 
 
 
 
 28 
 
 
 L. 
 
 2 
 
 6 
 
 12 
 
 9 
 
 
 
 I 
 
 30 
 
 M. 
 
 S. 
 
 
 
 
 
 
 I 
 
 2 
 
 
 
 L. 
 
 I 
 
 2 
 
 4 
 
 I 
 
 
 
 
 8 
 
 N. 
 
 S. 
 
 4 
 
 2 
 
 13 
 
 13 
 
 S 
 
 3 
 
 8 
 
 48 
 
 
 L. 
 
 I 
 
 I 
 
 10 
 
 7 
 
 3 
 
 
 2 
 
 24 
 
 P. 
 
 S. 
 
 
 
 S 
 
 4 
 
 2 
 
 I 
 
 2 
 
 14 
 
 
 L. 
 
 
 
 3 
 
 6 
 
 4 
 
 
 3 
 
 16 
 
 Rob. 
 
 S. 
 
 i6 
 
 4 
 
 10 
 
 II 
 
 I 
 
 2 
 
 
 44 
 
 
 Iv. 
 
 2 
 
 1 
 
 8 
 
 7 
 
 I 
 
 I 
 
 
 20 
 
 Rog. 
 
 S. 
 
 
 I 
 
 4 
 
 5 
 
 S 
 
 3 
 
 
 18 
 
 
 Iv. 
 
 
 I 
 
 21 
 
 6 
 
 3 
 
 
 I 
 
 32 
 
 Se. 
 
 S. 
 
 8 
 
 4 
 
 II 
 
 14 
 
 10 
 
 3 
 
 2 
 
 52 
 
 
 L. 
 
 I 
 
 19 
 
 40 
 
 29 
 
 3 
 
 
 
 92 
 
 Sh. 
 
 S. 
 
 
 
 2 
 
 2 
 
 4 
 
 
 4 
 
 12 
 
 
 I/. 
 
 
 I 
 
 9 
 
 3 
 
 4 
 
 
 I 
 
 18 
 
 T. 
 
 s. 
 
 8 
 
 5 
 
 II 
 
 13 
 
 10 
 
 2 
 
 2 
 
 SI 
 
 
 L. 
 
 6 
 
 II 
 
 24 
 
 6 
 
 I 
 
 4 
 
 
 52 
 
 Total, 
 
 
 78 
 
 95 
 
 251 
 
 17s 
 
 76 
 
 27 
 
 36 
 
 738' 
 
WEBER'S LAW TO SMELL. 
 
 55 
 
 It will be seen^that there is very little variation in the value 
 of A r from class to class of substances. All of Zwaardemaker's 
 
 classes are represented among either the solids or the liquids 
 except Class IX, that of nauseating smells. We could not 
 obtain Anagyris fcetida or Indian stink- wood (" Scatolholz ") 
 in the American market, and we did not try soon enough 
 to get it from Europe. Variations in the results of individual 
 subjects are, however, due to variations in the substances used. 
 
 Tablb VI. 
 
 Approximate Values of Isr arranged to show Variations for 
 r 
 Different Substances. 
 
 PART I. SOWDS. 
 
 Substance. 
 
 Number of 
 
 cases! equal to or j 
 I. approximating J 
 
 Total 
 number 
 of cases. 
 
 
 >MA) 
 
 K2) 
 
 i(3) 
 
 -K4) 
 
 Ks) 
 
 K6) 
 
 <KZ) 
 
 Yellow -wax. I, 
 
 
 
 1 
 
 3 
 
 4 
 
 
 
 
 8 
 
 Russian leather. I, 
 
 2 
 
 4 
 
 3 
 
 5 
 
 6 
 
 I 
 
 
 21 
 
 Oil of mace. II, 
 
 25 
 
 II 
 
 10 
 
 4 
 
 
 
 
 50 
 
 Cocoa-butter. II (?), 
 
 
 3 
 
 2 
 
 5 
 
 5 
 
 3 
 
 5 
 
 23 
 
 Rosewood. II, 
 
 I 
 
 
 10 
 
 10 
 
 2 
 
 I 
 
 
 24 
 
 Cedar. II, 
 
 
 
 9 
 
 2 
 
 3 
 
 
 4 
 
 18 
 
 Tolu balsam. Ill, 
 
 
 
 2 
 
 8 
 
 6 
 
 2 
 
 2 
 
 20 
 
 Gum benzoin. Ill, 
 
 6 
 
 2 
 
 8 
 
 6 
 
 5 
 
 2 
 
 I 
 
 30 
 
 Musk-root. IV, 
 
 
 I 
 
 6 
 
 7 
 
 2 
 
 I 
 
 3 
 
 20 
 
 Black rubber. V, 
 
 
 I 
 
 4 
 
 5 
 
 6 
 
 4 
 
 6 
 
 26 
 
 Gray rubber. V, 
 
 
 2 
 
 4 
 
 10 
 
 5 
 
 
 I 
 
 22 
 
 AsafcEtida. V, 
 
 14 
 
 6 
 
 5 
 
 
 
 
 
 25 
 
 Gum ammoniac and gutta- 
 
 • 
 
 
 
 
 
 
 
 
 percha. 
 
 
 
 
 
 
 
 
 
 (i) Weaker cylinder fr. 
 
 
 
 
 
 
 
 
 
 Utrecht, 
 
 I 
 
 3 
 
 4 
 
 3 
 
 2 
 
 
 I 
 
 14 
 
 (2) Stronger cylinder fr. 
 
 
 
 
 
 
 
 
 
 Utrecht, 
 
 I 
 
 I 
 
 5 
 
 7 
 
 I 
 
 I 
 
 
 16 
 
 (3) Home-made cylinder, 
 
 10 
 
 2 
 
 I 
 
 
 I 
 
 
 I 
 
 IS 
 
 Paraffine. VII, 
 
 
 
 
 3 
 
 3 
 
 2 
 
 
 8 
 
 Mutton-tallow. VII, 
 
 
 
 5 
 
 3 
 
 4 
 
 
 
 12 
 
 Glycerine soap. 
 
 
 
 2 
 
 4 
 
 
 I 
 
 I 
 
 8 
 
 Total, 
 
 60 
 
 37 
 
 83 
 
 86 
 
 51 
 
 18 
 
 25 
 
 360 
 
 Values for oil of mace, asa- 
 
 
 
 
 
 
 
 
 
 foetida, and home-made 
 
 
 
 
 
 
 
 
 
 cylinder of gum ammo- 
 
 
 
 
 
 
 
 
 
 niac and gutta-percha. 
 
 49 
 
 19 
 
 16 
 
 4 
 
 I 
 
 
 I 
 
 90 
 
 Final result. 
 
 II 
 
 18 
 
 67 
 
 82 
 
 50 
 
 18 
 
 24 
 
 270 
 
56 GAMBLE : 
 
 Tabi<B VI. — Continued. 
 Approximate Values of Ar arranged to show Variations for 
 r 
 Different Substances. 
 
 PART II. LIQUIDS. 
 
 Substance. 
 
 Number of cases { ,JZl\^JL. 1 
 l approximating J 
 
 _. aj en 
 
 a « 
 
 
 >KA) 
 
 5(2) 
 
 K3) 
 
 K4) 
 
 K5) 
 
 K6) 
 
 <KZ) 
 
 
 Oil of camphor. II, 
 
 I 
 
 7 
 
 26 
 
 8 
 
 6 
 
 
 4 
 
 52 
 
 Caryophylline. II, 
 
 I 
 
 2 
 
 lO 
 
 5 
 
 2 
 
 
 
 20 
 
 Oil of anise. II, 
 
 
 
 6 
 
 I 
 
 I 
 
 
 
 8 
 
 Valerianic acid. II, 
 
 lo 
 
 7 
 
 12 
 
 2 
 
 
 
 
 31 
 
 Ethyl butyrate. II, 
 
 3 
 
 12 
 
 8 
 
 6 
 
 
 
 
 28 
 
 Citral. II, 
 
 
 8 
 
 26 
 
 9 
 
 I 
 
 
 
 44 
 
 Vanilline. Ill, 
 
 
 
 ID 
 
 7 
 
 I 
 
 4 
 
 2 
 
 24 
 
 Coumarine. Ill, 
 
 3 
 
 II 
 
 34 
 
 31 
 
 7 
 
 
 3 
 
 89 
 
 Heliotropine. Ill, 
 
 I 
 
 4 
 
 14 
 
 
 6 
 
 I 
 
 I 
 
 30 
 
 Musk. IV, 
 
 
 2 
 
 IS 
 
 6 
 
 I 
 
 
 
 24 
 
 Allyl sulphide. V, 
 
 
 s 
 
 3 
 
 8 
 
 
 
 
 16 
 
 Pyridin. VI, 
 
 
 
 2 
 
 2 
 
 
 4 
 
 
 8 
 
 Laudanum. VIII, 
 
 
 
 2 
 
 I 
 
 
 
 I 
 
 4 
 
 Total, 
 
 i8 
 
 58 
 
 i68 
 
 89 
 
 25 
 
 9 
 
 II 
 
 378 
 
 PART III. SOLIDS AND LIQUIDS. 
 
 Nature of Stimulus. 
 
 Number of cases! ^"i"^!.*" °J \ 
 \ approximating / 
 
 Total 
 number 
 of cases. 
 
 
 >KA) 
 
 K2) 
 
 i(3) 
 
 K4) 
 
 Ks) 
 
 K6) 
 
 <KZ) 
 
 Solid, 
 Liquid, 
 
 II 
 18 
 
 18 
 58 
 
 i^I 
 
 82 
 89 
 
 50 
 25 
 
 18 
 
 9 
 
 24 
 II 
 
 270 
 378 
 
 Total, 
 
 29 
 
 76 
 
 235 
 
 171 
 
 75 
 
 27 
 
 35 
 
 648 
 
 Almost all the values for solids in which A r exceeds J^ were 
 
 r 
 obtained with asafoetida, oil of mace, or the home-made cylin- 
 der of gutta-percha and gum ammoniac. Thus, out of 9 values in 
 which D. exceeded % for solids, 7 were found with oil of 
 mace, and out of 16 values in which Rob. exceeded %, 10 were 
 found with the home-made cylinder of gutta-percha and gum 
 ammoniac, and 4 with oil of mace. We believe that it is per- 
 fectly fair to exclude these cylinders from our final results. 
 And if we do so there is little variation from substance to sub- 
 stance. The odor of asafcetida and oil of mace was very per- 
 ceptible when the instrument was closed, and the mace would 
 
240 
 
 WEBER'S I<AW TO SMELL. 
 
 I J i i 
 
 57 
 
 <i 
 
 240 
 
 180 
 
 160 
 
 140 
 
 80 
 
 60 
 
 40 
 
 Ar 
 
 Curves Showing the Approximate Vai,ues of — in the whole 
 
 Course of Experiments by the Method of Just Noticeable 
 
 Differences. (See Table VI, Part 3.) 
 
 The heavy line gives the values for both solids and liquids ; the 
 dotted line gives the values for solids, and the broken line for liquids. 
 The ordinates give the number of cases, and the abscissae approximate 
 
 va'-'-^" 
 
58 GAMBLE : 
 
 scrape off on the iiihaling-tube. While Zwaardemaker's mix- 
 ture of gum ammoniac 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 difEerence- 
 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 sur- 
 prising that the values of A r run higher for them than for 
 
 r 
 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 yi as the most common value, we must con- 
 clude that the value of Ar lies somewhere between yi and }{. 
 r 
 
 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 parafBne 
 appeared when a strong stimulus was given with coumarine. 
 T. said that heliotropine smelled like heliotrope on the left 
 (the better) side of her nose, and like bitter-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 nos- 
 tril. 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 "scat- 
 tered." 
 
 Section j. 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 labora- 
 tory-hours. It is needless to say that the instrument was 
 manipulated entirely by the experimenter. 
 
WEBER S I^AW TO SMELL. 
 
 59 
 
 Table VII. 
 Results of the Modified Form of the Method of Just Noticeable 
 Differences. 
 
 ^ 
 
 
 
 t^ 
 
 12 .^ 
 
 
 
 
 
 1 
 
 1 
 
 & 
 
 SUB- 
 STANCE. 
 
 METHOD 
 AND 
 
 
 
 Arc' 
 
 Aro" 
 
 Aru" 
 
 Aru' 
 
 Aro 
 
 Aru 
 
 Ar 
 
 Ar 
 
 \k 
 
 
 Standard 
 
 I? 
 
 s^ 
 
 
 
 
 
 
 
 
 
 D. 
 
 Gray 
 rubber, 
 
 (C. M.\ 
 
 \r=i9/ 
 
 R. 
 
 4 
 
 9 
 
 11 
 
 8 
 8 
 
 6 
 3 
 
 lO 
 
 7 
 
 9 
 lo 
 
 8 
 5 
 
 8'A 
 
 2 
 
 3 
 
 
 
 fc. M. i 
 
 lr=39/ 
 
 R. 
 
 4 
 
 i8 
 
 9 
 
 3 
 
 11 
 
 14 
 
 7 
 
 lOj^ 
 
 4 
 
 
 
 L,. 
 
 
 i8 
 
 9 
 
 4 
 
 8 
 
 14 
 
 6 
 
 lO 
 
 4 
 
 
 
 {llf.) 
 
 R. 
 
 4 
 
 
 
 
 
 2 
 
 6 
 
 4 
 
 S 
 
 
 
 Iv. 
 
 
 
 
 
 
 7 
 
 6 
 
 65^ 
 
 3 
 
 
 
 fjN Dl 
 
 lr=39/ 
 
 R. 
 
 4 
 
 
 
 
 
 12 
 
 lO 
 
 11 
 
 4 
 
 
 
 Iv. 
 
 
 
 
 
 
 9 
 
 lO 
 
 9J^ 
 
 4 
 
 K. 
 
 Rose- 
 
 {,=.-} 
 
 R. 
 
 .S 
 
 I,") 
 
 .S 
 
 2 
 
 11 
 
 lO 
 
 7 
 
 %y.. 
 
 3 
 
 
 wood, 
 
 Iv. 
 
 
 11 
 
 6 
 
 3 
 
 i6 
 
 9 
 
 lO 
 
 ci'A. 
 
 2 
 
 
 
 {?=:.} 
 
 R. 
 
 4 
 
 14 
 
 4 
 
 5 
 
 8 
 
 9 
 
 7 
 
 
 5 
 
 
 
 Iv. 
 
 
 12 
 
 6 
 
 9 
 
 14 
 
 9 
 
 12 
 
 IOJ4 
 
 4 
 
 
 
 {5=5} 
 
 R. 
 
 2 
 
 lO 
 
 5 
 
 7 
 
 lO 
 
 8 
 
 9 
 
 8K 
 
 .S 
 
 
 
 JU. 
 
 
 8 
 
 7 
 
 8 
 
 4 
 
 8 
 
 6 
 
 7 
 
 3 
 
 
 
 re. M. \ 
 
 U=42i" 
 
 R. 
 
 2 
 
 10 
 
 6 
 
 3 
 
 9 
 
 8 
 
 6 
 
 7 
 
 6 
 
 
 
 L. 
 
 
 11 
 
 6 
 
 4 
 
 lO 
 
 9 
 
 7 
 
 8 
 
 .S 
 
 
 
 /JNDl 
 \r=22j 
 
 R. 
 
 
 
 
 
 
 9 
 
 9 
 
 9 
 
 3 
 
 
 
 JL,. 
 
 
 
 
 
 
 13 
 
 15 
 
 14 
 
 A 
 
 
 
 /JNDI 
 
 I r=42 / 
 
 R. 
 
 
 
 
 
 
 8 
 
 i6 
 
 12 
 
 4 
 
 
 
 L. 
 
 
 
 
 
 
 7 14 1 
 
 loyi 
 
 4 
 
 Table VIII. 
 
 Results obtained for Red Rubber by the True Method of Minimal 
 
 Changes. 
 
 SUBJECT — SH. 
 
 r=io mm. 
 
 .A -a-o 
 
 Ar='l^ra.va.. 
 
 Gradation =2 mm. 
 A^=lK,mm. 
 
 rx 
 
 given before 
 
 r. 
 
 
 
 r given before ri. 
 
 
 Aro< 
 
 Aro" 
 
 Aro 
 
 Aro' 
 
 Aro" 
 
 Aro 
 
 R. N. 
 
 6 
 
 6 
 
 6 
 
 12 
 
 6 
 
 9 
 
 L.N. 
 
 6 
 
 lO 
 
 8 
 
 6 
 
 8 
 
 7 
 
 
 Aru' 
 
 Aru" 
 
 Aru 
 
 Aru' 
 
 Ar«" 
 
 Aru 
 
 R.N. 
 
 12 
 
 6 
 
 9 
 
 6 
 
 12 
 
 9 
 
 L.N. 
 
 8 
 
 4 
 
 6 
 
 8 
 
 12 
 
 lO 
 
 
 Ar 
 
 
 Ar 
 
 
 Ar 
 
 
 Ar 
 
 R. N. 
 L.N. 
 
 7i 
 7 
 
 
 r 
 
 •4+ 
 
 9 
 
 8i 
 
 
 «sr4 
 
 Pinal result : R. N. Ar=8i mm. Ar= 
 
 i+ 
 
 L. N. Ar=7| mm. Ar=U=i+ 
 r 
 
6o 
 
 GAMBLE : 
 
 Zwaardemaker concluded that for a standard of from 2 to 5 
 cm., the difference limen was about 1.5 cm., and that for a 
 standard of from 5 to 9 cm., it was about 3.5 cm. This would 
 make the value of A r run from about }i to about ^. Our 
 
 r 
 own results agree fairly well with his, and are a very pretty 
 confirmation of the results obtained by the method of just 
 noticeable differences. The writer intends to use the method 
 of minimal changes much farther. 
 
 In contrast with these excellent results are those of the 
 next Table : 
 
 Table IX. 
 Results obtained by the Method of Right and Wrong Cases. 
 
 SUBJECTS — C, D., K., N., ROB., ROG., AND T. 
 
 Instrument — Standard Olfactometer. Substances — Black Rubber 
 or Tolu Balsam. 
 
 r- AND r^. 
 
 Right 
 Cases. 
 
 Wrong 
 Cases. 
 
 Mistakes made in 
 
 TAKING THE Second 
 
 Stimulus for 
 
 Weaker 
 
 when Stronger. 
 
 Total 
 Number 
 
 OF 
 
 Cases. 
 
 20 and 25 
 50 and 70 
 20 and 30 
 30 and 50 
 20 and 40 
 30 and 60 
 20 and 50 
 20 and 60 
 
 37 
 30 
 47 
 33 
 42 
 
 4 
 39 
 
 7 
 
 19 
 10 
 
 19 
 II 
 22 
 
 2 
 II 
 
 I 
 
 12 
 
 il 
 
 5 
 18 
 
 8 
 
 I 
 
 56 
 40 
 66 
 44 
 
 'I 
 
 The stimuli given were never equal, and the judgment 
 ' ' equal ' ' was counted a mistake. The results of all the sub- 
 jects are massed. 
 
 As we said before, while exhaustion makes the errors nearly 
 all run in one direction, confusion due to the unfamiliarity of 
 olfactometric work is probably most at fault. More experi- 
 ments should be made with the standard olfactometer and 
 trained subjects. It is dificult to use the large olfactometer 
 with this method, because the intervals between stimuli must 
 be made very long or the subject can guess from the time spent 
 in manipulation how they have been changed. 
 
 As a rough method of testing the applicability of the method 
 of right and wrong cases to smell, we blind-folded one subject, 
 stopped his ears with absorbent cotton, and required him to tell 
 which way we had moved from a given standard on the large 
 olfactometer. The results are given in the following Table : 
 
wbbbr's law to smell. 
 
 6i 
 
 Table X. 
 
 Results of a Rough Attempt to Gauge the Applicability of the Method 
 
 of Right and Wrong Cases to Smell. 
 
 SUBJBCT— K. 
 
 
 SUBSTANCE- 
 
 ETHYI< BTJTYRATE 
 
 
 t 
 cd 
 
 y 
 
 1 
 
 S 
 
 03 
 
 || 
 go 
 n 
 
 M 
 
 ■31 . 
 
 Is 
 
 CO 
 
 •s 
 
 1 
 
 a; 
 bo 
 
 a 
 
 ed 
 
 .a 
 
 
 HI 
 
 
 il 
 
 I 
 
 i2 
 
 a 
 
 II 
 
 u ^ 
 0*0 
 
 u 
 
 a 
 
 w 
 
 fl.a 
 ii'3 g 
 
 IT 
 
 01 
 V 
 
 in 
 
 3 
 
 
 
 u 
 
 U 
 
 s 
 a 
 
 Mm. 
 
 2Q to 30 
 
 20 to 10 
 
 95 
 115 
 
 46 
 27 
 
 II 
 6 
 
 152 
 
 148 
 
 Mm. 
 40 to 60 
 60 to 40 
 
 100 
 106 
 
 35 
 29 
 
 6 
 5 
 
 141 
 140 
 
 We see that here again the number of mistakes "Was very- 
 large. Yet these were the last experiments made with A'. , 
 who had worked for us twice a week throughout the year, and 
 who had used butyric ether successfully in experiments by 
 the method of just noticeable differences. He was, however, 
 very tired at the time these last experiments were made. The 
 second stimulus still is more often mistakenly taken for 
 the weaker than for the stronger, showing that in these ex- 
 periments also exhaustion outweighed adhesion and the time- 
 error put together. (The tube was cleaned after every eight 
 comparisons.) 
 
 Summary and Conclusion. 
 
 In beginning our investigations, we saw that we could not 
 isolate simple olfactory qualities, and that an attempt to prove 
 "Weber's law for smell was justified only by the assumption 
 that it might apply to fusions. We also saw that the fact 
 that some olfactory qualities show but few grades of intensity 
 pointed to a rise towards the terminal intensity by geometrical 
 progression. Although Zwaardemaker explains the fact partly 
 by the supposition that different smells have different differ- 
 ence-limina, we believe that two smells with the same differ- 
 ence-limen may exhaust the human sense-organ with very 
 unequal degrees of rapidity, so that one may reach the termi- 
 nal intensity much sooner than the other. 
 
 Aside from the condition of the sense-organ, the intensity of 
 a smell depends (i) on the amount of odorous surface exposed 
 to the air, (2) on the time that it is exposed, (3) on the condi- 
 tion of the air in regard to temperature, moisture, etc. , which 
 controls the rate of evaporation, (4) on the diffusion-rate of the 
 

 
 
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