835 



SKELETON. 



SKELETON. 



other ; the lower are in contact with the cartilages that form the rest 

 of the groundwork of the nose. The anterior surface is concave from 

 above downwards, and convex from side to side ; the posterior has 

 opposite directions, and in the middle line, where the two bones are 

 in contact, is applied on the nasal spine of the frontal, and the edge 

 of the perpendicular plate of the ethmoid bone. 



The Superior Maxillary or Upper Jaw Bones (figs. 9, 10, 18, A) form 

 the greater part of the front of the face. Fig. 19 gives a view of the 

 outer part of that of the left aide. This surface is bounded below by 

 a narrow border, the Alveolar Border or Process (1), in which the 

 upper teeth are set in their sockets. Its outline is an elliptical arc, 

 and from it the outer surface ascends to the orbit, of which it forms 

 the inner and great part of the lower margin (2). It is unevenly 

 depressed in two or three places for the attachment of muscles of the 

 face. At the outer part, near the orbit, it presents a rough surface, 

 the Malar eminence (8), by which it is united with the cheek-bone. 

 Below and in front of this is a depression called Fossa Canina, and 

 on its inner side, just below the orbital margin, is the infra-orbital 

 foramen, through which the superior maxillary nerve passes to the 

 face. The anterior border of this external surface first ascends verti- 

 cally where the two bones are in contact in the middle line (Jig. 9) ; 

 then is suddenly cut out in a crescentic arch (4), so as to leave between 

 the two the large aperture into the nasal cavities, and then again 

 ascends where the upper maxillary bone unites with the nasal of the 

 same side. This ascending part is called the Nasal Process (5) ; its 

 summit is fixed in the nasal notch of the frontal bone; its outer sur- 

 face look* towards the orbit, is deeply grooved, and with the lachrymal 

 bone, to which its posterior border is attached, forms a channel for the 

 lachrymal duct ; its inner surface is directed towards the cavity of the 

 nose, has an oval roughness which is united with the inferior turbi- 

 nated bone, and above closes some of the anterior ethmoidal cells. 

 Below and behind the malar eminence the surface is excavated to form 

 part of the zygomatic fossa ; and above this it swells out, and is per- 

 forated by numerous foramina, through which the nerves of the upper 

 teeth pass. 



Fig. 19. 



The upper, or orbitar, surface (6), consists of a thin plate, forming 

 the floor of the orbit, and presenting a groove which leads to the 

 infra-orbital canal, and a depression for the insertion of the inferior 

 oblique muscle of the eye. The under or palatine surface is rough 

 and concave, and forms part of the roof of the mouth. Ita outer 

 border is arched, and bounded by the alveolar process ; the inner is 

 straight, and i set against that of the opposite side in the middle 

 line ; the posterior is united with the corresponding process of the 

 palate bone. The inner or nasal aspect presents below a rough sur- 

 face, by which the bone is united to its fellow on the opposite side, 

 and which is deeper in front than behind. It is surmounted by a 

 ridge which extends from before backwards, and between which and 

 that of the other bone is a narrow groove to receive the vomer. The 

 anterior part of the ridge (7) is called the Anterior Nasal Spine, and 

 cloae by it is the Foramen Incisivum, which leads down to the roof 

 of the mouth, and transmits the anterior palatine nerve. On the 

 outer aide of the ridge is a concave smooth surface, the upper surface 

 of the palatine process, of which the lower surface forma, as already 

 said, the roof of the mouth. From the outer part of this surface, 

 which forms part of the floor of the nostrils, the bone rises almost 

 vertically towards the nasal spine and the inner edge of the orbital 

 plate, and, at about its middle, presents a large aperture leading into 

 the Antrum Highmori, a cavity occupying the whole interior of the 

 body of the bone. 



The Palate Bones (Jig. 20) are placed backward between the superior 

 maxillary and the pterygoid processes of the sphenoid. The lower hori- 

 zontal or palatine portion (1) of each is attached behind the palatine 

 process of the upper jaw, to which it is similar in form, and it completes 

 the back part of the roof of the mouth, or hard palate, and of the 

 floor of the nostrils. Its posterior border has the Velum Palati 

 [PALATK] attached to it : its under surface presents two foramina, 

 through which the posterior palatine nerves pass. From its outer 

 border a thin plate (2) ascends vertically ; where it commences there 

 is, behind, a rough process (3), articulating with and filling up the gap 

 >etween the pterygoid processes of the sphenoid. (Fig. 16, a, 4, 4.) 

 The nasal or inner surface of this ascending portion articulates with 

 the inferior turbinated bone, and forms part of the outer wall of the 

 nostrils ; the outer surface articulates with the back and inner part 

 of the superior maxillary bone, and forms with it the posterior palatine 



canal The upper border haa a notch, which, in the entire skull, is 

 completed by the sphenoid bone into a hole, called the Spheno-Palatine, 

 for the transmission of nerves of the same name : behind it is a 

 triangular process (5), of which one surface articulates with the body 

 of the sphenoid ; and before it is another (4), of whose surfaces one 

 closes some of the ethmoid cells, and another forms a small part of 

 the back and floor of the orbit. 



The Malar, or Cheek Bones (figs. 9, 10, 18, t) form the most prominent 

 part of the cheeks. The form of each is quadrangular. The front 

 surface is slightly convex, and has small apertures for vessels and 

 nerves : the back covers the front of the zygomatic fossa ; the upper 

 surface is the narrowest, and forms part of the floor of the orbit, of 

 which also part of the front border is formed by the upper margin of 

 this bone. By its posterior surface and inner border the malar ia 

 united to the upper jaw-bone, as already described; and by its posterior 

 and outer angle to the zygomatic process of the temporal bone (fig. 

 14, 6), with which it forms the zygoma. 



The Lachrymal Bones (fig. 10, j) are two small thin lamellae of bone 

 at the fore part of the inner wall of the orbit. Each of them in some 

 measure resembles a thumb-nail, whence they are also called Ungual 

 Bones. Each is composed of two parts : the anterior is deeply grooved 

 on the surface turned towards the orbit, and contributes to the forma- 

 tion of the lachrymal canal with the nasal process of the upper jaw- 

 bone, with which its anterior margin articulates. The posterior part 

 is flat, and closes those of the ethmoidal cells which lie anterior to 

 its orbital plate. The posterior margin of this part articulates with 

 the ethmoid bone, the upper with the orbital plate of the frontal, and 

 the lower with that of the upper jaw-bone. 



The Inferior Turbinated or Spongy Bones are thin rough lamellae, 

 whose lower border is rolled up somewhat like a scroll. They lie 

 within the nasal cavities, and, except in being larger, they closely 

 resemble the bonea of the same name which are appended to the 

 ethmoid. They are attached at either end to the inner surfaces of 

 the nasal processes of the upper jaw and palate bones, and, in the 

 middle, to the lachrymal and the lower portion of the orbital plate of 

 the ethmoid bone : upon theae they are suspended before the aperture 

 of the Antrum, which, in the entire skull, they nearly conceal. Like 

 all the bones which form part of the cavities of the nose, they are 

 covered by mucous membrane. Beneath their outer concave surface 

 runs the inferior meatus of the nose. 



The Vomer (fig. 9, it) is a thin quadrilateral plate which forms a 

 considerable part of the middle partition of the nose. Ita upper border 

 ia the thickest, and is articulated with the azygos process and under 

 surface of the sphenoid bone ; the lower border fita into the groove 

 between the ridges in the apposed surfaces of the palatine processes 

 of the upper jaw and palate bones ; the anterior joins the vertical pnrt 

 of the ethmoid above, and the cartilaginous part of the septum of the 

 nose below : the posterior ia free, and divides the pasaage from the 

 noatrila into the pharynx behind. 



The Inferior Maxillary, or Lower Jaw-Bone (figs. 9, 10, 1, and fig. 21), 

 has a form something like that of a horse-shoe. It is made up of a 



body or horizontal portion (1), and a ramus or ascending portion (2). 

 The former is convex anteriorly, and on its very front presents the 

 prominence which contributes to form the chin (3). This is marked 

 in the middle line by the Symphysis, at which the two portions of 

 which the jaw was first composed are united. On either side of this 

 is a slight depression, the Foaaa Incisiva ; and farther out a hole, the 

 mental (4), through which branches of the inferior dental nerve and 

 vessel.-) pass to the chin. A raised line, giving insertion to muscles, 

 passes hence obliquely outwards to the upper border; and on the 



