Morphology of the Human Lachrymal Bone, $c. 245 



in the distorted crania of Peruvians it is most oblique. The following 

 table exhibits concisely these divergences : 



Comparing these it will be seen that the average internasal width 

 of the negroes raises their indexes, while the outward splay of the 

 lower third is greatest among the Peruvians. The bone is also 

 generally smaller in negroes than in the other races. 



XI. Comparative Anatomy and Morphology. The lachrymal bone 

 is a splint developed in the membrane overlying the outer side of the 

 ethmoid, and in mammals it is formed in close relation to the nasal 

 duct. I have not found, in any human embryos, specimens young 

 enough to show the earliest stages of the formation of the duct, but 

 my examinations of sections of this region in rats and pigs confirms 

 the description of the development of the duct given by Born and 

 Legal (" Morph. Jahrbuch," viii, 1882, p. 353), according to whom 

 it arises, not as Coste believed, by the closure of the surface 

 over the persistent oculo-nasal groove, but by the in-projection 

 of a column of epithelial cells from the surface in the line between 

 the eye and the nose, the column becoming afterwards bridged by 

 mesoblast, and developing a lumen. This agrees with the mode of 

 development observed among the lower Vertebrates by B.orn. Before 

 any trace of ossification appears in man the duct has a distinct 

 lumen. 



The formation of a double nasal duct is thus easily explicable, as 

 produced by the interjection of a vertical fold of mesoblast into the 

 column of cells. In the one instance of this very rare condition met 

 with by me in the dissecting room, and now in the Cambridge 

 Museum, there was a septum in the lachrymal sac, not quite dividing 

 it into two, nor stretching above the level of the vestibule, this was 

 continued into the nasal duct, completely dividing it for its upper 

 fourth, each surface being clothed with ciliated epithelium. The 

 septum ceased about the middle of the duct, ending obliquely, and 

 from this to the inferior opening the tube was single, but its lower 



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