904 
MR. A. FRASER ON THE DEVELOPMENT OF THE 
ferent tissue ready to become cartilage, and union takes place between it and the 
orbicular apex of the hyoidean rod. 
Semmer (11) corroborates Reichert’s conclusions respecting the origin of the malleus 
and incus. He describes the stapes as appearing in the form of an oval group of cells 
situated immediately behind and above the proximal end of the stylo-hyal and only 
indistinctly separate from it. 
It is, however, clearly separated from the long crus of the incus by the upper wall 
of the tympanic sulcus, and by a thick layer of indifferent tissue. It is in all proba¬ 
bility developed out of the second visceral arch ; but it is impossible to prove that, 
owing to the second visceral cleft having already disappeared. 
Hunt (12) considers them to arise in embryonic connective tissue elements. He 
does not mention whether they are continuous with any cartilage or not; he cannot 
accept Mr. Parker’s views respecting the stapes, but describes it as arising, like the 
other ossicles, in embryonic connective tissue elements. 
Gruber (13) agrees with Parker as to the stapes and fenestra ovalis. He does not 
accept the view that the cartilages give origin to the other ossicles, but considers them 
to be developed, like the stapes, from the original substance of the head vertebras. 
Lowe (14) describes all three ossicles as having been at one time continuous ; also, 
as having their origin in a visceral cartilage, but from which cartilage he does not 
make clear. 
Kolliker (15) accepts Reichert’s conclusions respecting the malleus and incus, 
but differs from him and from more recent workers respecting the origin of the stapes. 
He describes the hyoidean cartilage as being at its commencement a thin, elongated rod, 
stretching from, and continuous with, the cartilaginous petrous bone to the middle line 
in front, the cartilages of opposite sides failing, however, to meet there. The changes 
that take place at a later period are that the upper and the lower ends ossify to form 
the styloid process and the lesser cornu of the hyoid bone, while the connexion between 
these may be fibrous, cartilaginous, or bony. The origin of the stapes he leaves doubt¬ 
ful, but he denies altogether the contentions of Parker and Gruber that it springs 
from the labyrinth in the cartilaginous condition, as well as those of Reichert, that it 
forms a part of the hyoidean cartilage, although the cartilage and the stapes are very 
close to one another. 
SaleNsky’s (16) papers form the last contribution to the working out of this subject 
in the Mammalia (Pig and Sheep embryoes to which his observations were restricted), 
and I shall therefore state them in detail. In 2 centim. embryoes the mandibular and 
hyoidean cartilages are cylindrical in shape and limit the hyomandibular cleft, the 
one above, the other below. They attach themselves to the ear capsule and their 
extremities are connected by embryonic tissue. The changes that rapidly take place 
at the proximal extremity of the mandibular cartilage are, that it thickens and bends 
downwards, two furrows making their appearance, which divide the extremity into 
three parts, the posterior of which forms the elements of the body and long crus of the 
