Olfactory illusions are very rare in healthy people and are hence of
small importance. They are frequent among the mentally diseased, are
connected in most cases with sexual conditions and then are so vivid
that the judge can hardly doubt the need of calling in the physician.
Certain poisons tend to debauch the olfactory sense. Strychnine, e.g.,
tends to make it finer, morphine duller. People with weak lungs try, in
most cases, to set their difficulty of breathing outside themselves and
believe that they are inhaling poisoned air, coal-gas, etc. If one
considers in this connection the suspiciousness which many people
suffering from lung trouble often exhibit, we may explain many
groundless accusations of attempted murder by stifling with poisonous or
unbreathable gas. If this typical illusion is unknown to the judge he
may find no reason for calling in the physician and then--injustice.
The largest number of olfactory illusions are due to imagination.
Carpenter’s frequently cited case of the officials who smelled a corpse
while a coffin was being dug up, until finally the coffin was found to
be empty, has many fellows. I once was making an examination of a case
of arson, and on approaching the village noted a characteristic odor
which is spread by burned animals or men. When we learned that the
consumed farm lay still an hour’s ride from the village, the odor
immediately disappeared. Again, on returning home, I thought I heard the
voice of a visitor and immediately smelled her characteristic perfume,
but she had not been there that day.
Such illusions are to be explained by the fact that many odors are in
the air, that they are not very powerfully differentiated and may hence
be turned by means of the imagination into that one which is likely to
be most obvious.
The stories told of hyper-sensitives who think they are able to smell
the pole of a magnet or the chemicals melted into a glass, belong to
this class. That they do so in good faith may be assumed, but to smell
through melted glass is impossible. Hence it must be believed that such
people have really smelled something somewhere and have given this odor
this or that particular location. Something like this occurs when an
odor, otherwise found pleasant, suddenly becomes disgusting and
unbearable when its source is unknown. However gladly a man may eat
sardines in oil he is likely to turn aside when his eyes are closed and
an open can of sardines is held under his nose. Many delicate forms of
cheese emit disgusting odors so long as it is not known that cheese is
the source. The odor that issues from the hands after crabs have been
eaten is unbearable; if, however, one bears in mind that the odor is the
odor of crabs, it becomes not at all so unpleasant.
Association has much influence. For a long time I disliked to go to a
market where flowers, bouquets, wreaths, etc., were kept because I
smelled dead human bodies. Finally, I discovered that the odor was due
to the fact that I knew most of these flowers to be such as are laid on
coffins--are smelled during interment. Again, many people find perfumes
good or bad as they like or dislike the person who makes use of them,
and the judgment concerning the pleasantness or unpleasantness of an
odor is mainly dependent upon the pleasantness or unpleasantness of
associative memories. When my son, who is naturally a vegetarian and who
could never be moved to eat meat, became a doctor, I thought that he
could never be brought to endure the odor of the dissecting room. It did
not disturb him in the least, however, and he explained it by saying: “I
do not eat what smells like that, and I can not conceive how you can eat
anything from the butcher shops where the odor is exactly like that of
the dissecting room.” What odor is called good or bad, ecstatic or
disgusting, is purely a subjective matter and never to be the basis of a
universal judgment. Statements by witnesses concerning perceptions of
odor are valueless unless otherwise confirmed.