OF THE VOMEE, ETHMOID, AHD INTERMAXILLAEY BONES. 
291 
appearances is to be found principally in the sphenoidal spongy bones. These curious 
little bones reach their maximum of development at a very early age. Of four speci- 
mens beside me illustrating this condition, No. 1 (Plate IV. fig. 1) is from an infant pos- 
sibly about a year old; No. 2 (fig. 2) from a child two or three years old; No. 3 (fig. 3) 
from a child which, judging from the appearances of the rest of the skull, may have 
been four years old ; and No. 4 from an infant a few months old. In all these cases 
the body of the presphenoid is distinguishable from the postsphenoid by a mark at the 
line of junction, and projects forwards in continuation of it, in a somewhat rounded 
form, presenting little of that compression which has taken place to so great an extent 
in the adult. The presphenoid at this date is quite unconnected with the sphenoidal 
sinuses, and consists simply of the body just described, and the wings of Ingkassias. 
The body dips between the sphenoidal spongy hones, but is separated from them by 
some thickness of tissue. In Nos. 1 and 2, the sphenoidal spongy bones are already 
adherent to the ethmoid ; in 3 and 4 they are unattached either to the sphenoid 
or ethmoid. They are of the shape of hollow pyramids with their apices directed 
backwards, and their inner aspects parallel to their fellows. Their cavities (the com- 
mencing sphenoidal sinuses) open at their bases in front into the nasal fossae. 
There are, I believe, three distinct ossifications which go to the formation, normally, 
of each sphenoidal spongy bone: certainly there are three portions which require 
description. A superior plate, very distinctly marked off in the specimens alluded to, 
hmits the sphenoidal sinifs' more or less perfectly on the superior and internal aspects ; 
it forms a convexity directed upwards and inwards, and lies in contact with the fibrous 
tissue which separates it from the body of the sphenoid. An inferior plate forms the 
whole or the greater part of the floor of the sphenoidal sinus, and may be said to be the 
only recognizable part in the adult. Internally this plate comes in contact with the 
lower margin of the superior plate, beneath which it is prolonged downwards so as to lie 
edge to edge with the corresponding lamina of the vomer, immediately in front of the 
thick dilated part. Posteriorly it lies above the sphenoidal process of the palate-bone. 
Besides these two plates, there enters properly into the formation of the sphenoidal 
spongy bone a third element (an orbital plate) connected with the anterior and external 
part of the inferior plate, and whose characteristic property is that by an aspect which 
articulates behind with the sphenoid, in front with the ethmoid, inferiorly with the 
palatals, and sometimes above with the frontal, it takes a small part in the formation of 
the orbit. It may be attached to the ethmoid, palatal, or sphenoid hone, instead of to 
the remainder of the sphenoidal spongy hone. In specimen No. 3 it is certainly un- 
usually large and distinct, but it can be easily distinguished in Nos. 1 and 2 also. It is 
absent in No. 4 ; but there it exists incorporated with the orbital process of the palate- 
bone, at least that process projects upwards between the sphenoid and ethmoid. This 
enlarged form of the orbital process of the palate-bone is not at all uncommon ; and that 
it arises from union with it of the orbital element of the sphenoidal spongy bone I am 
satisfied, from its occupying the position of that element. Moreover, in an adult speci- 
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