ractive to their fellow-citizens are
often repulsive to a certain proportion of those who come near them,
as, for instance, is the case with the extract of the East Indian herb
"patchouli." In regard to our other senses there is a general
agreement amongst mankind, which extends also to all animals, as to
what is agreeable and what is disagreeable. There are definite
mathematical laws as to harmony and melody in sound and colour which
affect animals and ourselves to a large extent similarly. Sweets are
agreeable and bitters are disagreeable, though it is the fact that the
snail, which loves sugar, recoils from saccharine, and there are
"mites" (_Acari_) which feed with avidity on bitter strychnine! Excess
of heat and of cold is disliked by animals and all men, whilst the
sense of touch is pleasurably or painfully affected in much the same
way in most men and animals, more than is the case with regard to any
other of the senses. The sense of smell depends upon immediate and
personal experience of "association" for the determination of pleasure
or pain, attraction or repulsion, as the result of its being called
into operation. It is a very general experience that odours are more
efficient in arousing memory than are mere colour effects or sounds.
Not only in animals with acutely developed olfactory powers, but also
in man, an odour--a peculiar perfume--will start a whole chain of
reminiscence when sight and sound have failed to do so. It is due to
this close association with memory (conscious or unconscious) that an
odour is agreeable or disagreeable.

In itself an odour is neither attractive nor repulsive. The acrid
fumes of sulphur, chlorine, ammonia, and such bodies are not simply
"odours" but corrosive chemical vapours, which act painfully upon the
nerves of common sensation within the air-passages of the nose and
throat and not exclusively, if at all, on the terminations of the
olfactory nerves. An odour--that which acts on the special nerves of
smell distributed in chambers of the nose--acquires its attractive or
its repulsive quality only as the result of mental association with
what is beneficial (suitable food, mates, friends, safety, home, the
nest), or with what is injurious (unsuitable food, poison, enemies,
danger, strange surroundings, solitude). Hence it is intelligible that
the man accustomed to garlic or onions in his food is strongly
attracted by their smell. So too the man whose tribe or companions
hav