OSTEOLOGY. O / 



the orbicularis palpebrarum is attached. Above this it 

 gives partial attachment to labii superioris alseque nasi, 

 below to nasalis longus labii superioris. The posterior or 

 orbital plate is funnel-shaped, converging from all points 

 to towards the lachrymal foramen^ situated just behind the 

 centre of the marginal border. To this bone near this 

 foramen is attached the inferior oblique muscle of the eye- 

 ball, and in it rests the lachrymal sac from which the 

 ductus ad nasum is continued forwards through a bony 

 canal, running along and attached to the internal surface 

 of the facial plate of the bone. The i7iner surface of the 

 bone assists in forming the superior maxillary sinus, and is 

 therefore covered with mucous membrane. The anterior 

 margin is in contact with os nasi and also with the supe- 

 rior maxillary bone, which extends along the whole length 

 of the inferior margin, along the inner edge, while the 

 malar bone has a squamous union with a considerable por- 

 tion of the outer edge. The extreme posterior part of this 

 margin is smooth. The superior margin has a squamous 

 union with os f rontis, but at the posterior angle, where this 

 margin and the inferior meet, the lachrymal bone comes in 

 contact with os palati. 



OS PALATI forms the anterior, posterior, and outer 

 boundary of the posterior naris. It is very irregular, but 

 mainly consists of a bony plate elongated from behind 

 forwards. This plate is convex on its internal surface, and 

 posteriorly is divided into two equal parts by a prominent 

 ridge. The upper part is articulatory supero-posteriorly 

 for union with the lateral part of the body of ethmoides ; 

 in front of this os f rontis occupies a small space ; os 

 lachrymale, a still smaller ni front of that ; but the greater 

 part of this division is covered with mucous membrane, 

 assisting to form the ethmoid sinus. Below the articula- 

 tion with OS f rontis is foramen spheno-palati7ium, which is 

 continued by a groove on to the inferior part, which, with 

 the inferior part of the ridge, posteriorly is united to the 

 ])terygoid and (more inwardly) the vomer. Anteriorly 

 this part becomes much prolonged and is smooth and 

 concave, forming the posterior boundary of the posterior 

 nares. It becomes twisted from below upwards at its 

 anterior extremity, thus forming a peculiar process, 

 palatine, the inner margin of which is smooth, rounded, 

 concave, and coated with mucous membrane forming the 



