OF THE VOMEE, ETHMOID, AND INTEEMAXELLAET BONES. 
295 
purchased with disarticulated skulls, is formed by an atrophied ala of the vomer, or by 
the edge of the central plate of the ethmoid projecting to one side, which it may do in 
an infinite variety of ways. 
The same cause accounts for the imperfect description of the inferior margin of the 
vomer. In particular, the projection which lies on the crista incisiva is very liable to 
be destroyed by anchylosis ; and even when it is not anchylosed it often requires very 
careful disarticulation to exhibit it. Sometimes the crista itself undergoes changes. It 
may have the margins of its groove worn away, and present a flat surface having the 
fore part of the vomer imbedded between its halves; or it may be completely bent over 
to one side, so that one semicrista shall lie above the other, while the fore part of the 
vomer, lying between them, is necessarily distorted, but may yet admit of disarticulation. 
At an early age the united margins of the maxillaries behind the anterior palatine canal 
become elevated into a sharp ridge, and the margins of the originally flat surface of the 
vomer in contact with them bend down to grasp it, and become irregular, thin away, 
and disappear more or less completely. Vestiges of them, as they die away, may some- 
times be seen still very distinct on careful disarticulation, even in adult subjects. The 
edges of the palate-bones often form a more prominent ridge than the maxillaries, rising 
into a spine a couple of lines or more in height ; and the portion of vomer in contact 
with this is a thin edge. 
These remarks, I believe, are sufiicient to show that if the human vomer is to be 
described with accuracy in its character as a separate bone, it must be studied as it 
shows itself in early life *. 
If it be asked why, even in the early condition, when its form and connexions most 
resemble the typical aiTangement, the human vomer should yet differ from the arrange- 
ment in other mammals by having the arch of communication between it and the 
ethmoid a separate bone, some explanation will be arrived at by considering that in 
Man the ethmoid is very feebly developed, and that the distance between the ethmoid 
and vomer is increased, — circumstances which depend on the feeble development of the 
sense of smell, and on the rapid curvature of the arch of the cranium. To the cursory 
glance the human ethmoid presents a rather well-developed appearance, since it forms a 
large part of the inner wall of the orbit, and the orbital plate is a peculiarity confined to 
Man and the Quadrumana. Yet in Man the ethmoid is rudimentary, and in Monkeys 
still more so ; and the existence of the orbital plate is a mere consequence of the great 
curvature of the cranial arch. In the generality of mammals the ethmoid is shielded 
by the frontal and palatals ; but in Man the palatals are removed from it by the down- 
ward development of the face ; while by the great size of the anterior lobes of the brain 
it is pushed from under the shelter of the frontal, and the cribriform plate is depressed 
into the horizontal plane, instead of occupying, as in the Cat, the Sheep, &c., an almost 
vertical position. But whereas in most mammalia the lateral masses of the ethmoid 
• Of this the first Moxeo was well aware. See the Works of Alexaxdeb Moneo, M.D., published by 
his son in 1781, p. 120. 
