OF THE VOMEE, ETHMOID, AND INTEEMAXILLAEY BONES. 
305 
Man, Take, for example, the Cat (tig. 7, B & C). The posterior aspect of the body 
of the presphenoid in the Cat exactly corresponds to the anterior extremity of the 
postsphenoid, presenting an appearance exactly similar to what the body of a vertebra 
exhibits on removal of its epiphyses ; viz. a part in the middle, broad below and narrow 
above, formed by the centrum, and the two superior angles formed by the alee. If we 
look at the same bone from the front, we see plainly that the septum between the sphe- 
noidal sinuses consists entirely of the anterior extremity of the centrum greatly com- 
pressed; and just as the posterior extremity of the presphenoidal centrum is continuous 
with the postsphenoidal, so is its anterior extremity continuous with the septal cartilage 
of the nose and the central plate of the ethmoid. This continuity is in some respects 
even better seen in the new-born Kitten, as above described. Now we know that, 
morphologically, it is of little importance whether cranial bones are developed in the 
primordial cartilage of the skull, of which the septal cartilage is the remains, or are 
developed round it. The basisphenoid in fishes, for example, is developed round it, 
while in mammals it is developed in it. Therefore the central plate of the ethmoid, 
the vomer, and the mesial processes of the intermaxillaries all claim from their 
position to be centra as much as the basioccipital and basisphenoid. With regard 
to the mesial processes of the intermaxillaries, that they play the part of a centrum 
is shown, not merely by their constant relation to the septal cartilage, but by their 
articulation with the vomer being of such a description as to make them continuous 
with that bone both on the upper and under aspect, and by their condition in cleft- 
palate. 
2. The vomer, lateral masses of the ethmoid, and palate-bones belong to one segment. 
This seems to be an altogether unavoidable conclusion, from the constant connexion of 
these bones in so invariable a manner. 
What meaning can be attached to the remarkable way in which, in the human sub- 
ject, the vomer and lateral masses of the ethmoid, notwithstanding their altered forms 
and positions, preserve the relations to one another which they exhibit in other animals, 
but that they are members of one segment 1 And how else can we explain that the place 
of the flattened ethmoid and ethmovomerine laminae of the Dugong is occupied in the 
Delphinidae by expansions of the vomer, which both form the posterior walls of the 
nostrils and articulate with the palatals 1 
This conception of the construction of the ethmoidal segment, as well as the reasons 
just mentioned for considering that the mesial-palatine processes of the intermaxillaries 
play the part of a centrum, is at variance with the view of Professor Goodsie, that the 
vomer and the intermaxillaries are members of one “sclerotome*.” 
Also if the connexions of the vomer and lateral masses of the ethmoid recorded above 
are considered sufficient to prove that these bones are parts of one segment, it will at 
once appear evident that the lateral masses of the ethmoid and the ethmovomerine 
laminse form an incomplete neural arch. In that case we must differ from Professor 
* Op. cit. p. 138. 
2 T 
MDCCCLXII. 
