OSTIA NASOLACRIMAL^ IN MAN 



189 



reference to the adult types of ostia nasolacrimal. The embry- 

 ology of the nasolacrimal passages demonstrates that the point 

 of coalescence of the strand of epidermal cells with the mucous 

 membrane of the lateral wall of the meatus nasi inferior is incon- 

 stant. The place of coalescence may be at the most cephalic 

 point of the meatus nasi inferior (fig. 12). On the other hand, 



Concha nasalis 

 inferior 



Meatus nasi 



inferior 

 Ductus naso- 

 lacrimal 



Figs. 12 and 13 Outline drawings of frontal sections (from human embryos) 

 through the region of the developing nasolacrimal passages. Note in fig. 12 that 

 the strand of epidermal cells, the anlage of the nasal end of the ductus nasolacri- 

 mal, has coalesced with the mucous membrane of the nose at the most cephalic 

 portion of the meatus nasi inferior. In fig. 13 the point of coalescence is farther 

 caudal on the lateral wall of the meatus nasi inferior. The ductus nasolacrimal 

 is represented in the drawing as solid (see previous paper as to the time and manner 

 of canalization of the duct). 4 



the point of coalescence may be much farther caudal on the lateral 

 wall of the meatus nasi inferior (fig. 13). There is also consider- 

 able variation in the ventro-dorsal plane. 



The point of coalescence of the strand of epidermal cells with 

 the nasal mucous membrane, of course, determines the position 

 of the adult ostium nasolacrimal (figs. 6 and 11). The manner 

 of this early coalescence also materially influences the type of 



4 Loc. cit. 



