378 MAMMALIAN ANATOMY 



velopment of the surrounding bones, and especially of the os planum 

 of the ethmoid, the lachrymal exhibits few noteworthy variations. 



In some specimens the anterior-superior angle is prolonged upward 

 into a long spine, the swollen lip of which forms the greater part of 

 the lachrymal tubercle. 



The lachrymal groove is rarely only faintly marked. It is usually 

 perforated by two or three foramina in the upper part and by one or 

 two in the root of the hamulus below ; it may be, however, irregularly 

 cribriform. 



In one lachrymal examined the anterior border was joined to the 

 hamulus, producing a true lachrymal foramen. The hamulus itself 

 may be thin or thick ; the malar surface is, therefore, sometimes linear, 

 sometimes quadrate. 



HUMAN LACHRYMAL BONE. 



The lachrymal bone of man (Fig. 296) is almost identical with the 

 lachrymal of the cat. It differs from the latter in being relatively 



narrower from before backward, in not articulating by 

 its anterior-inferior angle with the malar, and in ar- 

 ticulating behind with the constant os planum of the 

 ethmoid, and on the inside more distinctly with the 

 lachrymal process of the maxillo-turbinal and the 

 uncinate process of the lateral ethmoid. Its internal 

 RIGHT LACHRYMAL surface completes the so-called lachrymal cells of the 



BONE. EXTERNAL 



VIEW. ethmoid. 



1, orbital surface; THE VOMER. 



2, lachrymal groove ; 



3, hamuius; 4 frontal General Description. The Vomer is a delicate 



border ; 5, ethmoidal 



border; 6, maxiiiary symmetrical rod, forming the lower part of the septum 



border; 7, process ar- J 



with the ^hich divides the two nasal chambers. It is a direct 



maxillo-turbinal bone. 



continuation forward of the base of the cranium, 

 inasmuch as it articulates behind with the anterior end of the sphe- 

 noid (Fig. 298). Its grooved upper surface receives the lower edge of 

 the mesethmoid and the cartilaginous nasal septum. Its under surface 

 is thickened in front and joins the upper surfaces of the horizontal 

 plates of the maxillary and palatine bones. At the posterior part, the 

 sides are laterally expanded, causing the bone to assume the shape of 

 a prostrate cross. The upper part of the cross, which is the posterior 

 part of the bone, is compressed from above downward, and the lower 



