FACE. 



The structure is compact, except near its 

 upper and lower angles, where there is some 

 eancellous tissue. 



Developemetit.lls ossification commences 

 in one piece about the fiftieth day, and is com- 

 pleted at birth, when the bone appears thicker, 

 and its orbitar plate larger in proportion than 

 in the adult : its vertical diameter is, however, 

 narrow, and the malar holes are large. 



The wn.su/ bones (ossa nusi; Germ, die 

 Nasenbeine) form the upper part of the 

 nose, and are placed between the nasal pro- 

 cesses of the upper maxillary and below the 

 frontal bones, inclining from above downwards 

 and forwards. They have two surfaces, and 

 their form is quadrilateral, the vertical exceed- 

 ing the transverse diameter. They are stout 

 and narrow above, and thin and broader below. 

 The anterior or cutaneous surface is smooth, 

 covered by the integuments and pyramidalis 

 muscle, concave from above downwards, con- 

 vex transversely. An oblique hole for the 

 passage of vessels is usually found above the 

 centre of one or both nasal bones, and some 

 smaller foramina are scattered over the surface. 

 The posterior or pituitary surface is concave, 

 narrow, especially above, and lined by the 

 olfactory membrane, presenting grooves for 

 vessels and the internal orifice of the canal (or 

 hole) mentioned above. 



The borders are four : a superior, short, 

 thick, dentated, inclined from above down- 

 wards and backwards, and resting on the nasal 

 notch of the frontal bone between its two in- 

 ternal angular processes : the inferior border, 

 longer than the preceding, thin, jagged, in- 

 clining from the median line downwards and 

 outwards, and generally presenting about its 

 centre a slight notch for the passage for a fila- 

 ment of the nasal nerve. This border forms 

 the upper and front part of the anterior opening 

 of the nasal fossoe, and gives attachment to the 

 lateral cartilages of the nose. The external 

 border is the longest, and is cut obliquely for 

 its articulation with the nasal process of the 

 upper maxillary bone. The internal border is 

 shorter, thick and rough above, and thin be- 

 low : it forms, on the inner aspect of the bone, 

 in conjunction with the corresponding part of 

 the bone of the opposite side, a ridge and 

 groove for the reception of the nasal process or 

 spine of the frontal bone, and for the upper and 

 anterior border of the perpendicular plate of 

 the ethmoid. 



Connexions. The nasal bones articulate 

 with each other, with the frontal, ethmoid, and 

 upper maxillary bones, and with the lateral 

 cartilages of tlie nose : they form a part of the 

 cavity of the nose. 



Their structure is cancellous and thick above, 

 thin and compact below. 



Developement. They are perfectly ossified 

 at birth, when they are proportionally longer 

 than in the adult, corresponding in this respect 

 with the depth of the orbit and the smallness of 

 the anterior aperture of the nose. The ossifica- 

 tion of each nasal bone commences by a single 

 point about the beginning of the third month. 

 The lachrymal bones (ossa unguis v. fac/iry- 



mulia ; Germ, die Thranenbeine) are qua- 

 drilateral ill form, thin, seinitransparent, and 

 are situated on the anterior part of the inner 

 wall of the orbit between the ethmoid, frontal, 

 and upper maxillary bones ; they derive one 

 of their names from the resemblance which 

 they bear to a finger-nail. Each bone presents 

 two surfaces and four borders. 



The external or orbitar surface is divided at 

 its anterior third by a vertical crest, terminating 

 below in a little curved process which forms 

 the outer wall of the upper orifice of the nasal 

 canal ; in front of this crest the bone is per- 

 forated with numerous little holes, and its sur- 

 face is concave and forms with that of the 

 nasal process of the upper maxilla the canal 

 for the lachrymal sac. The posterior part of 

 this surface is smooth, nearly flat, and is 

 continuous with that of the os planum of the 

 ethmoid, which lies immediately behind it. 



The internal or ethmoidal surface is rough, 

 and is divided by a vertical groove, which 

 corresponds to the crest on the orbitar aspect 

 of the bone ; the anterior division is convex 

 and forms part of the middle meatus ; the pos- 

 terior division is in contact with the ethmoid 

 and contributes to close its cells. 



Of the four borders, the superior is the 

 shortest and thickest ; it is irregular and arti- 

 culates with the inner border of the orbitar 

 plate of the os frontis. The inferior is divided 

 into two parts by the lower extremity of the 

 crest already described on the anterior surface 

 of the bone ; in front of this the border de- 

 scends along a thin process or angle of the 

 bone, which is articulated with the inferior 

 turbinated bone, and contributes to form the 

 inner wall of the canal for the nasal duct ; 

 behind, this border is broad, and rests on the 

 inner margin of the orbitar plate of the upper 

 maxillary bone. The anterior border is slightly 

 grooved for the reception of the inner margin 

 of the posterior border of the nasal process 

 belonging to the upper maxilla. The posterior 

 border is thin and articulates with the anterior 

 edge of the os planum. The os unguis has 

 four angles, of which the anterior inferior is 

 remarkable for its length. 



Connexions. This bone articulates with the 

 frontal, the upper maxillary, the ethmoid, and 

 the inferior turbinated ; it contributes to form 

 part of the orbit of the cavity of the nose and 

 of the groove for the lachrymo-nasal duct. 

 It gives attachment to the reflected portion of 

 the tendon of the orbicularis palpebrarum, 

 and to the tendon of the tensor tarsi muscles. 

 In structure it is thin and compact. 

 Development. It is complete at birth, ex- 

 cept at its posterior superior angle, where there 

 is a deficiency between it and the frontal and 

 ethmoid bones, and where a separate piece is 

 sometimes formed. It is broader from back 

 to front in proportion, at this period of life, 

 than in the adult, and its lachrymal groove is 

 larger. Its ossification commences by a single 

 point between the third and sixth months. 



A small lachrymal bone has been described 

 as sometimes found at the lower part of the 

 os unguis; and not uufrequently some separate 



