odorous stimuli are also extremely sensitive to tactile stimuli; this is,
for instance, the case with the snail, in whom at the same time olfactive
sensibility seems to be spread over the whole body.[24] The sense of smell
is gradually specialized, and when taste also begins to develop a kind of
chemical sense is constituted. The organ of smell, however, speedily
begins to rise in importance as we ascend the zoölogical scale. In the
lower vertebrates, when they began to adopt a life on dry land, the sense
of smell seems to have been that part of their sensory equipment which
proved most useful under the new conditions, and it developed with
astonishing rapidity. Edinger finds that in the brain of reptiles the
"area olfactoria" is of enormous extent, covering, indeed, the greater
part of the cortex, though it may be quite true, as Herrick remarks, that,
while smell is preponderant, it is perhaps not correct to attribute an
exclusively olfactory tone to the cerebral activities of the _Sauropsida_
or even the _Ichthyopsida_. Among most mammals, however, in any case,
smell is certainly the most highly developed of the senses; it gives the
first information of remote objects that concern them; it gives the most
precise information concerning the near objects that concern them; it is
the sense in terms of which most of their mental operations must be
conducted and their emotional impulses reach consciousness. Among the apes
it has greatly lost importance and in man it has become almost
rudimentary, giving place to the supremacy of vision.

Prof. G. Elliot Smith, a leading authority on the brain, has well
summarized the facts concerning the predominance of the olfactory
region in the mammal brain, and his conclusions may be quoted. It
should be premised that Elliot Smith divides the brain into
rhinencephalon and neopallium. Rhinencephalon designates the
regions which are pre-eminently olfactory in function: the
olfactory bulb, its peduncle, the tuberculum olfactorium and