GENESIS OF NASOLACRIMAL PASSAGES IN MAN 



13 



the right side of the same embryo both lacrimal-duct anlages are 

 equally developed. 



To say, from the condition found in the embryo represented 

 in figs. 12 and 13, that the superior lacrimal-duct anlage is a por- 

 tion of the original mother cord of cells is I believe erroneous. 

 I rather hold, in such cases, that the inferior-duct anlage is tardy 

 in its development, and that both ducts have their anlages in 

 buds from the mother cord. Of course as stated above one or 

 the other duct may at times, for unknown reasons, fail to develop 

 far enough to gain coalescence with the free border of the eyelid; 



Figs. 12 and 13 Photomicrographs of frontal sections of a human embryo aged 

 forty-two to forty-five days, in the region of the early lacrimal passages of the 

 left side. Note that the superior lacrimal duct (sld) is well advanced. The only 

 evidence of an inferior duct is seen in fig. 12, at point marked A'. Whether this 

 early condition would have led to an absence of the inferior lacrimal duct is of 

 course not known, sld = superior lacrimal duct ; x = anlage (?) of inferior lacrimal 

 duct. X 32. 



or the duct may reach the border of the lid but fail to establish 

 a lumen at this point. Cases have also been reported in which 

 supernumerary lacrimal puncta and lacrimal ducts were present 

 (Weber and others). There are at times small buds arising from 

 the lacrimal-duct anlages, and in all probability these at times 

 continue to develop independently until they reach and gain 

 coalescence with the eyelids. The lumina for these super- 

 numerary lacrimal ducts are, of course, established just as they 

 are in the regular ducts. 



