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MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE, 107 
Il.—Zhe Accessory Organ of Jacobson. 
At 8, in fig. 1 of Plate VI, a minute tube is shown in transverse 
section, which extends alongsidethe groove which, at the bottom of 
the nasal cavity, is contained between the septum and the alveolar 
process of the superior maxilla. This tube is shielded, as is shown 
in the figure, partly by the lower extremity of the osseous lamella 
that forms the support of the lower conchanarium. It, z.¢. the 
tube, is met with as far as the tube of Jacobson extends, and like 
this is bilateral. I will call it the “accessory organ of Jacobson ;” 
it is also flattened from side to side, and it includes a lumen 
varying in diameter, in hardened specimens, and in different 
places. In some places the lumen is a narrow slit, in others it 
is of relatively large transverse diameter. The wall of the tube 
consists of an epithelium and of a loose connective tissue, which 
above and below is thickest, and includes here a plexus of large 
vessels, arteries, and veins, extending chiefly in a longitudinal 
direction, @. e. parallel with the tube. 
The following are the measurements of the accessory organ, 
the epithelium only being here considered as the wall of the 
tube :—At a place exactly corresponding to that in fig. 1, the 
tube being much compressed from side to side, I find the breadth, 
t.e. the transverse diameter of the tube from side to side—lumen 
and epithelium of both sides—amounts to 0°144 mm., while the 
height of the tube, z.e. the transverse diameter across the upper 
and lower wall, is 0°63 mm. . 
At another place, further backward, where the tube appears of 
larger size, and with a much larger lumen, the breadth of the 
tube (lumen and epithelium of both sides) is 0°518 mm., while 
the height is 1:06 mm., the transverse diameter of the lumen 
being 0°38 mm. 
The epithelium lining the tube is stratified columnar epithe- 
lium, whose thickness is somewhat greater in the median wall, 
z.e. the wall nearer the nasal septum, than in the lateral wall. 
In the upper and lower sulcus it is slightly thicker than at the 
sides. At a place identical to that represented in fig. 1 the 
thickness of the epithelium of the median wall is 0-079 mm., 
that of the lateral wall 0°058 mm. At a place further in front, 
‘2.é. where the tube appears larger, the thickness of the epithe- 
lium of the median wall is 0:05 mm., of that of the lateral wall 
0-04 mm. 
The epithelium lining the iumen is the most conspicuous, and 
at the same time the thickest part of the wall. On its inner 
surface, i.e. the one facing the lumen, there exists a well 
marked cuticle, similar to that mentioned in the organ of Jacob- 
