ile) OSTEOLOGY. 
Architecture.—Formed of dense and compact bone, the strength of the nasal bones is 
increased by their mode of union and the formation of a median crest posteriorly. 
Variations.—The size and configuration of the nasal bones vary greatly in different races, 
being, as a rule, large and prominent in the white races, and flat and reduced in size, as well as 
depressed, in the Mongolian and Negro stock. Obliteration of the internasal suture is unusual ; 
it is stated to occur more frequently in negroes, and is the recognised condition in adult apes. 
Ossification.—The nasal bones are each developed from a single centre, which makes 
its appearance about the end of the second month in the membrane covering the fore 
part of the cartilaginous nasal capsule. Subsequent to birth the underlying cartilaginous 
stratum disappears, persisting, however, below in the form of the lateral nasal cartilage, 
and behind as the septal cartilage of the nose. 
THE LACHRYMAL BONES. 
The lachrymal bone (os lachrymale) or os unguis, a thin scale of bone about the 
size of a finger-nail, forms part of the imner orbital wall behind the frontal pro- 
cess of the superior maxilla. Irregularly quadrangular, it has two surfaces—an 
inner and outer—and four borders. 
Its external or orbital surface has a vertical ridge, the lachrymal crest (crista 
lachrymalis posterior), running downwards upon it. In front of this is the lachrymal 
Oeniesl santas groove (sulcus lachrymalis) for the lodgement of the lachrymal 
/ sac. The floor of this groove descends below the level 
4 of the bulk of the bone, and forms the descending process, 
7 _tachrymal Which helps to complete the osseous canal for the nasal 
Aas duct, and articulates inferiorly with the inferior turbinal. 
raclwymal The lower end of the lachrymal crest terminates in a 
: hook-like projection, the hamular process (hamulus lachry- 
malis), which curves round the posterior and outer edge 
nem of the lachrymal notch of the superior maxilla, and thus 
poses defines the upper aperture of the canal for the nasal duct. 
To the free edge of the crest behind the lachrymal groove 
are attached the reflected portion of the tendo oculi, and 
the tensor tarsi muscle. The part of the bone behind the 
lachrymal crest is smooth and continuous with the surface of the os planum of 
the ethmoid. The inner surface is irregular and cellular above; it closes in some 
of the anterior ethmoidal cells. Where it is smoother it forms a part of the 
lateral wall of the middle meatus of the nose immediately behind the frontal 
process of the superior maxilla, and above the inferior turbinated bone. The 
superior border articulates with the orbital plate of the frontal; the anterior edge 
with the posterior border of the frontal process of the superior maxilla, with 
which it completes the lachrymal groove for the lodgment of the lachrymal sae. 
The inferior margin articulates with the orbital surface of the superior maxilla, 
and in front, by its descending process with the inferior turbinal. Posteriorly the 
bone articulates with the anterior border of the os planum of the ethmoid. 
Fic. 105.—RicHr LACHRYMAL 
Bone (Orbital Surface). 
Connexions.—The lachrymal bone articulates with four bones—the frontal, ethmoid, inferior 
turbinal, and the superior maxilla. 
Architecture.—The bone consists of a thin papery translucent lamina, somewhat strength- 
ened by the addition of the vertical crest. 
Variations.—The lachrymal is occasionally absent. In some cases it is divided into two 
parts ; in others replaced by a number of smaller ossicles. In rare instances the hamular process 
may extend forwards to reach the orbital margin, and so bear a share in the formation of the face, 
as in lemurs (Gegenbauer). In other instances the hamulus is much reduced in size. Occasion- 
ally the lachrymal is separated from the os planum of the ethmoid by a down-growth from the 
frontal, which articulates with the orbital process of the superior maxilla, as is the normal 
disposition in the Gorilla and Chimpanzee. (Turner, Challenger Reports, “ Zoology,” vol. x. 
Part IV. Plate I.; and A. Thomson, Journ. Anat. and Physiol., London, vol. xxiv. p. 349.) 
Ossification.—The lachrymal is developed from a single centre, which makes its 
appearance about the end of the second or the beginning of the third month of intra- 
uterine life in the membrane around the cartilaginous nasal capsule. 
