158 



SKELETON OF THE DOG 



cavity. The posterior palatine and sph'eno-palatine foramina are situated further 

 back and a little lower; the former is immediately below the latter. A horizontal 

 plate extends from the inner surface, meets that of the opposite bone and com- 

 pletes the lamina transversalis spoken of in the description of the ethmoid bone. 

 There is no palatine sinus. 



The pterygoid bones are very wide and short. They form a considerable part 

 of the lateral boundaries of the posterior nares. The lower and posterior borders 

 are free and at their angle of junction there is a variable hamulus. 



The nasal bones are (in most breeds) long and wider in front than behind. 

 The external surface is variably concave in its length and is inclined toward the 

 median suture so as to form a central groove. The inner borders turn downward 

 and form an internal nasal crest which becomes very prominent behind. The pos- 

 terior parts fit into a notch formed by the frontal bones. The anterior ends form 

 an almost semicircular nasal notch. 



The lacrimal bone is very small. The facial part extends very little or not 

 at all beyond the orbital margin. The orbital surface is small and triangular, 



and presents the entrance to the lacri- 

 mal canal. 



The large zygomatic process con- 

 stitutes the bulk of the malar bone. 

 It is very long and is strongly curved. 

 The upper border is convex, free in 

 front, where it forms part of the orbital 

 margin, beveled behind for articulation 

 with the similar process of the temporal 

 bone. Between these it bears an emi- 

 nence, the processus frontalis, to which 

 the orbital ligament is attached. The 

 body of the bone may l)e considered to 

 consist of a lacrimal process directed 

 upward and fitting in l)etween the lacri- 

 mal and maxilla, and a maxillary pro- 

 cess directed downward. The facial 

 surface is convex. 



The superior turbinal bone is in its 



anterior part a simple plate, attached 



by one edge to the nasal bone; it curves downward and inward, and its free border 



is thickened and everted. The posterior part is wider and reseml^lcs the ethmo- 



turbinals, with which it is connected. 



The inferior turbinal bone is short and very complex. It is attached to the 

 nasal surface of the maxilla by a basal lamina, which divides into two secondary 

 lamellae. The latter detach numerous tertiary lamellae, which are coiled and have 

 thick free edges (Fig. 373). 



The vomer is not in contact with the posterior part of the floor of the nasal 

 cavity, and does not divi^le the posterior nares. The posterior end is narrow and 

 deeply notched. Near the posterior nares the two plates curve outward and join 

 the palate bones and assist in forming the lamina transversalis. 



The two halves of tlie mandible do not fuse completely even in old age. The 

 body presents six alveoli for tlie incisor teeth and two for the canines. The incisor 

 alveoli increase in size from first to third. The canine alveoli extend deeply down- 

 ward and backward. There are usually two or more foramina on the mental 

 surface. The rami diverge less than in the pig. The inferior border of the hori- 

 zontal part is convex in its length and is thick and rounded. The alveolar Ijorder 

 is slightly concave in its length and is a little everted, especially in its middle; 



Fig. 125. — Mandible of Dog, Right Anterior View. 

 a, Right ramus; b, left ramus; c, body; d, alveolar 

 border; e, processus angularis; /, condyle; f/, coronoid 

 process; h, masseteric fossa; (', k, crests which form the 

 upper and lower boundaries of fossa; /, mandibular fora- 

 men; m, mental foramina; )t, masseteric line; o, sigmoid 

 notch. (EUenberger-Baum, .\nat. d. Hundes.) 



