554 GEORGENA SWEET. 



this position, where it lies dorsal to the ophthalmic nerve, the 

 duct is definitely flattened, and is lined by columnar epithelium 

 with very darkly-staining nuclei, the irjucr border of the cells 

 of which appears slightly cuticular, while it is surrounded by 

 concentric fibres. The duct soon comes to lie nearer to the 

 middle line, and then sinks with a small artery, a veiulet, and 

 a small bundle of nerve-fibres from the ophthalmic nerve, 

 into a depression in the dorsal surface of the maxillary bone. 

 This becomes enclosed anteriorly forming a canal [12, fig. 5, 

 n.l.d.^ by which the duct now more cylindrical in shape, and 

 its accompanying structures may enter the inferior meatus of 

 the nose. About the level of the posterior end of the organ 

 of Jacobson it runs in a groove in the bony jaw, which forms 

 the lateral boundary of this part, and it is here flattened and 

 still lined by columnar epithelium. Its greatest diameter 

 (vertical) is, in this region, "25 mm. It then descends again 

 into a canal [12, fig. 4, n.l.d.l in the bone, which it leaves 

 opposite the Steuonian canals to lie near the bony floor of 

 the nasal cavity [12, fig. 3, ii.l.d.] with its artery and veins 

 between the premaxillary bone and the cartilage which forms 

 the floor of the nose in this anterior region. Immediately 

 behind the connection of the ali-nasal cartilao'C with the ven- 

 tral cartilages it runs towards the middle line embedded in a 

 gland mass, becoming more and more cuticular inside and 

 quite flat ('25 mm. iu greatest vertical diameter), until it 

 opens into the nasal furrow by an oblicpie aperture, on the 

 under surface of the small primary lateral ridge or "concha" 

 found near the external opening of the nose. 



With regard to the general course of this naso-lachryuuil 

 duct, for such it undoubtedly is, we may see by reference to 

 Klein's descriptions of this structure in the guinea-pig [7, 

 p. 224] and rabbit [7, p. 567], that it is here very similar to 

 Avhat he has described in those forms, as also its accomj)anying 

 artery and veins. He, however, has described the epithelium 

 as a stratified columnar layer, the columnar cells being next 

 the lumen of the duct, and more cubical cells outside this. I 

 find an identical appearance of nuclei, but consider that there 



