characteristics which mark the great and varied mass of sensations reaching the brain through the channel of the olfactory organ.  The main special character of olfactory images seems to be conditioned by the fact that they are intermediate in character between those of touch or taste and those of sight or sound, that they have much of the vagueness of the first and something of the richness and variety of the second.  AEsthetically, also, they occupy an intermediate position between the higher and the lower senses.[26] They are, at the same time, less practically useful than either the lower or the higher senses.  They furnish us with a great mass of what we may call by-sensations, which are of little practical use, but inevitably become intimately mixed with the experiences of life by association and thus acquire an emotional significance which is often very considerable.  Their emotional force, it may well be, is connected with the fact that their anatomical seat is the most ancient part of the brain.  They lie in a remote almost disused storehouse of our minds and show the fascination or the repulsiveness of all vague and remote things.  It is for this reason that they are—­to an extent that is remarkable when we consider that they are much more precise than touch sensations—­subject to the influence of emotional associations.  The very same odor may be at one moment highly pleasant, at the next moment highly unpleasant, in accordance with the emotional attitude resulting from its associations.  Visual images have no such extreme flexibility; they are too definite to be so easily influenced.  Our feelings about the beauty of a flower cannot oscillate so easily or so far as may our feelings about the agreeableness of its odor.  Our olfactory experiences thus institute a more or less continuous series of by-sensations accompanying us through life, of no great practical significance, but of considerable emotional significance from their variety, their intimacy, their associational facility, their remote ancestral reverberations through our brains.

It is the existence of these characteristics—­at once so vague and so specific, so useless and so intimate—­which led various writers to describe the sense of smell as, above all others, the sense of imagination.  No sense has so strong a power of suggestion, the power of calling up ancient memories with a wider and deeper emotional reverberation, while at the same time no sense furnishes impressions which so easily change emotional color and tone, in harmony with the recipient’s general attitude.  Odors are thus specially apt both to control the emotional life and to become its slaves.  With the use of incense religions have utilized the imaginative and symbolical virtues of fragrance.  All the legends of the saints have insisted on the odor of sanctity that exhales from the bodies of holy persons, especially at the moment of death.  Under the conditions of civilization these primitive emotional associations of odor tend to be dispersed, but, on the other hand, the imaginative side of the olfactory sense becomes accentuated, and personal idiosyncrasies of all kinds tend to manifest themselves in the sphere of smell.