robably the sperm-whale. It is a grey, powdery
substance, and in it are embedded innumerable fragments of the horny
beaks and sucker-rings of cuttle-fishes--creatures which form the
chief food of the sperm-whale and other toothed whales. I have already
mentioned above that one of our common cuttle-fishes (the _Eledone
moschata_) has a strong odour of musk, and it is possible that
ambergris owes its perfume to the musk-like scent of the cuttle-fish
eaten by the whale in whose intestine it is formed. Another "smell"
which is extremely mysterious is that produced by two quartz-pebbles,
or even two rock-crystals, or two pebbles of flint or of corundum,
when rubbed one against the other. A flash of light is seen, and this
is accompanied by a very distinct smell, like that given out by
burning cotton-wool. It is demonstrated--by careful chemical cleaning
before the experiment--that this is not due to the presence of any
organic matter on or in the stones or crystals used. It seems to be an
exception to the rule that "odours" (as distinct from pungent vapours
or gases) are only produced by substances formed by plants or animals.
Perhaps that is not so completely a rule as I was inclined to think.
It is true that one can distinguish the "smells" of chlorine, of
bromine, and of iodine from one another. And there are statements
current as to the distinctive smells of metals--though they may
possibly be due to the action of the metals on organic matter. In any
case it seems, according to our present knowledge, that the smell
given out by the rubbing of pieces of silica (quartz, flint, etc.) is
due to particles of silica (oxide of silicon) volatilised by the heat
of friction, which are capable of acting specifically on the olfactory
sense-organ.

CHAPTER XI

KISSES

"Among thy fancies, tell me this,
What is the thing we call a kiss?
I shall resolve ye what it is."

--Robert Herrick

Kissing is an extremely ancient habit of mankind coming to us from far
beyond the range of history, and undoubtedly practised by the remote
animal-like ancestors of the human race. Poets have exalted it, and in
these hygienic days doctors have condemned it. In the United States
they have even proposed to forbid it by law, on the ground that
disease germs may be (and undeniably are in some cases) conveyed by it
from one individual to another. But it is too deep-rooted in human
nature, and has a significance and origin too