brain. The olfactory lobe, from its
position, is sometimes called the _pallium basale_, and the hippocampal
formation the _pallium marginale_; and these two parts of the pallium
form what, on account of their phylogenetic history, Elliott Smith well
terms the _archipallium_. A fissure, the limbic fissure, marks off more
or less distinctly this archipallium from the rest of the pallium, a
remainder which is of later development and therefore designated by
Elliott Smith the _neopallium_. Of the archipallium, the portion which
constitutes the olfactory lobe is well formed in the selachian fish. In
the reptilian cerebrum the hippocampal region, the pallium marginale,
coexists in addition. These are both of them olfactory in function. Even
so high up in the animal scale as the lowest mammals they still form one
half of the entire pallium. But in the higher apes and in man the
olfactory portion of the pallium is but a small fraction of the pallium
as a whole. It is indeed so relatively dwarfed and obscured as to be
invisible when the brain is regarded from the side or above. The
olfactory part of the pallium exhibits little variation in form as
traced up through the higher animals. It is of course small in such
animals as Cetaceans, which are _anosmatic_. In highly osmatic such as
the dog it is large. The _uncus_, and _subiculum cornu ammonis_ of the
human brain, belong to it. Disease of these parts has been accompanied
by disturbance of the sense of smell. When stimulated electrically (in
the rabbit) the olfactory pallium occasions peculiar torsion of the nose
and lips (Ferrier), and change, often slowing or arrested, of the
respiratory rhythm. P.E. Flechsig has shown that the nerve-fibres of
this part of the pallium attain the final stage of their growth, that is
to say, acquire their sheaths of myelin, early in the ontogenetic
development of the brain. In the human brain they are myelinate before
birth. This is significant from the point of view of function, for
reasons which have been made clear especially by the researches of
Flechsig himself.

The completion of the growth of the nerve-fibres entering and leaving
the cortex occurs at very various periods in the growth of the brain.
Study of the development of the fibres entering and leaving the various
regions of the pallium in the human brain, discovers that the regions
may be conveniently grouped into those whose fibres are perfected before
birth and those whose fibres