GENESIS OF NASOLACRIMAL PASSAGES IN MAN 



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Kg. 1 Frontal section through the nasal fossa (./') and the now-rudimentary 

 naso-optic furrow (no), from a human embryo aged approximately thirty-three 

 days. Note that there is no evidence of thickening of the epidermis along the 

 floor of the rudimentary naso-optic furrow (no), to establish the anlage of the 

 nasolacrimal passages. X 62.4 



Fig. 2 A similar section to that illustrated in fig. 1, from a human embryo aged 

 thirty-four days. Note the plug-like thickening of the epidermis in the position 

 of the rudimentary naso-optic furrow. This is the first evidence of the anlage 

 of the nasolacrimal passages. X 62.4. 



Fig. 3 A corresponding section to those illustrated in figs. 1 and 2, from a 

 human embryo aged approximately thirty-five days. Note the marked in-growth 

 of the epidermal plug in comparison to the plug represented in fig. 2. X 62.4. 



Fig. 4 A frontal section through the anlage of the nasolacrimal passages, 

 from a human embryo aged forty -three days. Note that the cord of epidermal 

 cells is now entirely separated from the surface. It is wholly surrounded by 

 mesenchymal cells. In the sections preceding and following this the separation 

 from the surface was just as complete as in that shown here. X 62.4. 



The first evidences of the anlage of these passages I found in a 

 12 mm. embryo, aged about thirty-four days. The anlage is 

 well illustrated in figs. 2 and 7 as a plug-like thickening (in frontal 

 section) of the deeper layers of the epidermis along the floor of 

 the remains of the naso-optic fissure. Note especially that the 

 surface layer of flat epidermal cells is not included in the anlage 



