166 
ME. GrEOEG-E W. CALLENDEE ON THE FOEMATION AND 
sockets is far from perfect in a foetus 9 inches long, although the plate forming the 
inner wall of the middle incisor is complete in a foetus 6 '7. In the latter, too, the divi- 
sion between the bicuspids and molars begins to be apparent. 
The canine socket is formed in the body of the bone, the incisor sockets grow down 
below the incisor process, those of the bicuspid and molar teeth are alone connected 
with the distinct aveolar plate. 
The palatal-alveolar process in a foetus 4-3 has lost its uniform appearance on the 
nasal side. Plates of bone in waving lines have thickened the upper surface of the 
palate, and ascend the posterior margin of the groove on the inner side of the nasal 
process, and assist in forming the nasal duct. By the turning up of some of these bone 
plates, which are formed in the membrane extending from the ethmoid and inferior 
turbinate cartilage to the septum, that portion of the maxilla which is the inner wall of 
the antrum is now formed. A second plate, constituting the outer w T all of the antrum 
and part of the floor of the orbit, rises with an inward slope from the inner edge of 
the orbital process, whilst deposits of bone are accumulating on the orbit, chiefly on 
either side of the infraorbital fissure. The growing down of the alveolar walls alone 
marks the increase of this part of the bone on its palatal surface. The infraorbital 
fissure is still open in its entire length in a foetus 9 inches long, but in the anterior half 
of the orbital plate it forms a deep canal in consequence of the deposits of bone on its 
either side. 
The antrum is at first of large comparative size. In a foetus 4 - 3 its greatest width is 
nearly one-tenth of an inch, the palate being at this period just over one-tenth of an 
inch wide. In the adult, owing to the rising of the orbital plate and the hollowing out 
of the zygomatic process, the antrum is T2 inch wide to *7 for the palate. In a foetus 
nine inches long, in consequence of the rapid increase in the width of the palate, the 
antrum is only as T to - 2, but a deep fissure (Plate XIV. fig. 8) shows where the orbital 
plate is to be lifted up to allow of the lateral and vertical expansion of the cavity of the 
antrum. 
Of the Vomer and Intermaxillary Bones. 
These bones are developed in the membrane which covers the internasal cartilage, and 
forms part of the boundaries of the sides of the nostrils, Ossification is commonly said 
to commence in the posterior part of the vomer. This is not the case. In a foetus P5 
this bone consists of a keel from which spicula bud like ribs on either side of the carti- 
lage of the septum. Those in front are most advanced in their development, those 
behind diverge from each other as they pass backward, as is shown in fig. 4, Plate XIII., 
which represents the vomer of a foetus 2 '3. 
At the anterior extremity of the vomer the process of ossification extends to form the 
intermaxillary bones. 
These bones, though their appearances vary in different mammals, have amongst 
these animals certain common features. (1) The line of articulation with the superior 
