MINUTE ANATOMY OF ORGAN OF JACOBSON IN GUINEA-PIG. 223 
ciliated epithelium, like that of the nasal furrow. A little 
further back the epithelium lining the tube is uniform on 
all sides, being ciliated columnar epithelium, such as has 
been minutely described in my former paper as lining the 
lateral wall of the organ of Jacobson. 
Still further back (see fig. 6) we meet with this impor- 
tant alteration in the epithelium, that the median wall is 
lined with the thick sensory epithelium minutely described 
in my first paper. The tube, as a whole, has not, however, 
got yet its characteristic shape, ¢. e. so compressed from side to 
side, that its lumen is kidney shaped in transverse section (see 
figs. 1 and 2 in my first paper); this shape is, however, 
soon obtained, and’ the organ retains it to near its posterior 
extremity. Before this, however, is reached the direction 
of the lumen, and consequently of the walls, is more or less 
oblique and slanting downwards and inwards. In this 
oblique position we find chiefly the epithelium and the 
cavernous layer. 
As regards the structure of the wall of the tube of 
Jacobson in its commencement, it is similar to that of the 
nasal furrow, viz. the subepithelial membrane is connective 
tissue infiltrated with numerous lymph-corpuscles, and 
resembling more or less diffuse adenoid tissue. 
Already at the mouth of Jacobson’s tube (12 in figs. 4 
and 5) we find large veins forming a plexus and repre- 
senting the rudiment of. the cavernous tissue described in 
my first paper. This plexus becomes more developed as we 
pass backwards, and from its first appearance, ¢.e. at the 
mouth of Jacobson’s organ, to the posterior extremity of 
this (see below), does not encroach on the median wall, z.e. 
the wall nearest the septum. In the parts from which fig. 6 is 
taken, but not further in front, we find between the vessels 
of the cavernous tissue already bundles of non-striped mus- 
cular tissue. 
Longitudinal sections through the organ of Jacobson prove 
that a considerable posterior portion is without any carti- 
lage, and is enclosed altogether in the bone of the crista 
nasalis, as mentioned above. 
The posterior cecal extremity of the organ is slightly 
curved inwards and upwards; it is smaller in diameter than 
the rest of the organ ; its lumen is circular in cross section. 
The median wall of this extremity is not lined with any 
sensory epithelium, this having previously suddenly come 
to an end; we find here everywhere only columnar epithe- 
lium, similar to that of the lateral wall of the preceding parts. 
