168 
ME. GEORGE W. CALLENDER ON THE FORMATION AND 
wall of the middle and lateral incisor sockets is continuous, as previously stated, with 
the plate of bone which covers in the canine notch. 
In a foetus 4-3 the intermaxilla is completely formed and may be traced as a distinct 
bone (Plate XIV. fig. 6). It consists of the parts already described, which are continued 
backwards to form the front of the palate, filling up the notch between the incisor and 
palatal processes (Plate XIY. figs. 5 & 7), and of a narrow portion which ascends and fits 
by a convex surface into the groove of the nasal process, ending above at the ridge for 
the turbinate bone, part of which ridge it forms. In a foetus 2 - 3, and also in one 
3 inches long, two sets of bone-deposits are seen immediately in front of the vomer, one 
consisting of a fine process which projects in the middle line, the other formed of blocks, 
one above the other, which lie over the incisor process and add to its depth and strength. 
In a foetus 9 inches long these bone-formations have made but little progress, and may 
easily escape detection. 
In a foetus 9 inches long, either intermaxillary bone is in great part fused with its 
corresponding upper maxilla. The anterior edge of its nasal process has united to the 
nasal process of the maxilla, and its horizontal portion is inseparably attached to the 
upper surface of the incisor process, but the outline of the bone is preserved by a fissure 
(Plate XIV. figs. 9 & 10), which is traced along its posterior margin from the middle of the 
nasal process of the maxilla, and which deepens as it reaches the palate through which 
it extends, often permanently. At its upper extremity this line, widening into a groove, 
contains the remains of the bent edge of the anterior boundary of the nostril, which can 
be traced downwards for some distance along a kind of canal, and which in a foetus 6-5 
retains its connexion with the soft structures lying beneath the nasal process, reaching 
up towards the nasal bone. 
Lastly, in a foetus 9 inches long, the boundary of the intermaxilla is still distinctly 
marked on the under surface of the palate, extending outwards to the posterior half of 
the outer wall of the lateral incisor, which it forms as far as the margin of the foramen 
for the nerve, thence it extends, as a fissure occupied by the nerve for the middle incisor, 
and crossing the septum between the incisors is lost in the plates of bone which have 
joined the incisor process. 
The preceding observations account for the absence of all trace of the human inter- 
maxillary bone on the facial aspect of the upper jaw in the adult, whilst the permanent 
fissure through the palate and on the inner side of the nasal process are equally explained. 
The bone, in fact, is shut off from the face by the nasal and incisor processes of the supe- 
rior maxilla. Distinctly outlined (Plate XIY. fig. 6) at the close of the fourth month, it 
is joined to the superior maxilla during the latter part of the fifth or beginning of the 
sixth month ; its nasal process, as it may conveniently be termed, is buried in that of 
the upper jaw, the apex assisting to form a permanent ridge for articulation with the 
inferior turbinate bone. In a foetus L5 I notice a slight cleft in the nasal process of 
the superior maxilla corresponding with the top of the groove on its inner surface, but 
