e
face of an adjoining vertebra, and of a bony arch or ring which
encloses and protects the nervous cord. Oken supposed that there were
four such vertebrae in the skull, the centra being firmly fused and the
arches expanded to form the dome of the skull. Quite correctly, he
divided the skull into four regions, corresponding to what he called
an ear vertebra, at the back, through which the auditory nerves
passed; a jaw vertebra, in the sphenoidal region, through which the
nerves to the jaws passed; an eye vertebra in front, pierced by the
optic nerves, and again in front a nose vertebra, the existence of
which he doubted at first. Quite rightly, he discriminated between the
ordinary bones of the skull and the special structures surrounding the
inner ear which he declared to be additions derived from another
source. So far it cannot be doubted that the vertebral theory made a
distinct advance in our knowledge of the skull. It was to a certain
extent, however, thrown into disrepute by various fantastic theories
with which Oken surrounded it. Later on, Cuvier removed from it these
wilder excrescences, and amplified the basis of observation upon which
the underlying theory of the unity of type of the skull throughout the
vertebrates was based. Cuvier, however, came to reject the theory,
except so far as it applied to the posterior or occipital segment of
the skull. Later on, Owen resuscitated the theory, first throwing
doubt on the merit of Goethe, and then suggesting that Oken, instead
of relying on the observed facts, had deduced the whole theory from
his own imagination. Owen, although he made no new contribution to
fact or theory in this matter, practically claimed the whole credit of
it as a scientific hypothesis.

When Huxley took up the subject, the position was that the vertebral
theory was in full possession of the field, under the auspices of
Owen. Huxley began afresh from observed facts. The first object of his
investigation was to settle once for all the question as to whether
the skulls of all vertebrates were essentially modifications of the
same type. He took in succession the skulls of man, sheep, bird,
turtle, and carp, and showed that in all these there were to be
distinguished the same four basi-cranial regions: the basi-occipital,
basi-sphenoid, pre-sphenoid, and ethmoid. These were essentially
identical with the centra of the four vertebrae of Oken. Similarly, he
showed the composition of the lateral an