It thus comes about that the grosser manifestations of sexual allurement by smell belong, so far as man is concerned, to a remote animal past which we have outgrown and which, on account of the diminished acuity of our olfactory organs, we could not completely recall even if we desired to; the sense of sight inevitably comes into play long before it is possible for close contact to bring into action the sense of smell.  But the latent possibilities of sexual allurement by olfaction, which are inevitably embodied in the nervous structure we have inherited from our animal ancestors, still remain ready to be called into play.  They emerge prominently from time to time in exceptional and abnormal persons.  They tend to play an unusually larger part in the psychic lives of neurasthenic persons, with their sensitive and comparatively unbalanced nervous systems, and this is doubtless the reason why poets and men of letters have insisted on olfactory impressions so frequently and to so notable a degree; for the same reason sexual inverts are peculiarly susceptible to odors.  For a different reason, warmer climates, which heighten all odors and also favor the growth of powerfully odorous plants, lead to a heightened susceptibility to the sexual and other attractions of smell even among normal persons; thus we find a general tendency to delight in odors throughout the East, notably in India, among the ancient Hebrews, and in Mohammedan lands.

Among the ordinary civilized population in Europe the sexual influences of smell play a smaller and yet not altogether negligible part.  The diminished prominence of odors only enables them to come into action, as sexual influences, on close contact, when, in some persons at all events, personal odors may have a distinct influence in heightening sympathy or arousing antipathy.  The range of variation among individuals is in this matter considerable.  In a few persons olfactory sympathy or antipathy is so pronounced that it exerts a decisive influence in their sexual relationships; such persons are of olfactory type.  In other persons smell has no part in constituting sexual relationships, but it comes into play in the intimate association of love, and acts as an additional excitant; when reinforced by association such olfactory impressions may at times prove irresistible.  Other persons, again, are neutral in this respect, and remain indifferent either to the sympathetic or antipathetic working of personal odors, unless they happen to be extremely marked.  It is probable that the majority of refined and educated people belong to the middle group of those persons who are not of predominantly olfactory type, but are liable from time to time to be influenced in this manner.  Women are probably at least as often affected in this manner as men, probably more often.

On the whole, it may be said that in the usual life of man odors play a not inconsiderable part and raise problems which are not without interest, but that their demonstrable part in actual sexual selection—­whether in preferential mating or in assortative mating—­is comparatively small.