. The American journal of anatomy . all sure that this is the anlage of the inferiorduct. It is a well known fact that one or the other lacrimal-ductanlage may fail to reach the free border of the eyelid. It is,therefore, possible, had this embryo (figs. 12 and 13) continuedits development to term, that it would have been born withouta drainage duct for the inferior eyelid. On the other hand, on GENESIS OF NASOLACRIMAL PASSAGES IN MAN 13 the right side of the same embryo both lacrimal-duct anlages areequally developed. To say, from the condition found in the embryo representedin figs. 12 and 1
. The American journal of anatomy . all sure that this is the anlage of the inferiorduct. It is a well known fact that one or the other lacrimal-ductanlage may fail to reach the free border of the eyelid. It is,therefore, possible, had this embryo (figs. 12 and 13) continuedits development to term, that it would have been born withouta drainage duct for the inferior eyelid. On the other hand, on GENESIS OF NASOLACRIMAL PASSAGES IN MAN 13 the right side of the same embryo both lacrimal-duct anlages areequally developed. To say, from the condition found in the embryo representedin figs. 12 and 13, that the superior lacrimal-duct anlage is a por-tion of the original mother cord of cells is I believe rather hold, in such cases, that the inferior-duct anlage is tardyin its development, and that both ducts have their anlages inbuds from the mother cord. Of course as stated above one orthe other duct may at times, for unknown reasons, fail to developfar enough to gain coalescence with the free border of the eyelid;. Figs. 12 and 13 Photomicrographs of frontal sections of a human embryo agedforty-two to forty-five days, in the region of the early lacrimal passages of theleft side. Note that the superior lacrimal duct (sld) is well advanced. The onlyevidence of an inferior duct is seen in fig. 12, at point marked A. Whether thisearly condition would have led to an absence of the inferior lacrimal duct is ofcourse not known, sld = superior lacrimal duct; x = anlage (?) of inferior lacrimalduct. X 32. or the duct may reach the border of the lid but fail to establisha lumen at this point. Cases have also been reported in whichsupernumerary lacrimal puncta and lacrimal ducts were present(Weber and others). There are at times small buds arising fromthe lacrimal-duct anlages, and in all probability these at timescontinue to develop independently until they reach and gaincoalescence with the eyelids. The lumina for these super-numerary lacrimal ducts are, of course, est
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
