552 DR. E. KLEIN. 
Going alittle further back than fig. 2, we find that Jacobson’s 
cartilage changes in two ways: first, the curve itself is not any 
more the lowest point, but has become turned slightly inwards, 
2. é. in a median direction, and, secondly, there is an indication 
of its severance from the rest of the lower limb of the cartilage 
of the lateral wall of the nasal furrow. 
In fig. 3 both these changes are well shown. Still further back 
the severance is complete, and Jacobson’s cartilage forms now an 
independent and well-defined organ, of the shape and position 
shown very accurately in fig.3. Itis here noticed that the inner 
or median labium is considerably different in shape from that in 
fig. 2; it still terminates with an upper sharp margin next the 
septal cartilage, but is possessed of a short triangular 
projection. 
As is shown in fig. 3, the lower nasal furrow becomes invagi- 
nated into the concavity of Jacobson’s cartilage as the mouth of 
the organ of Jacobson, in exactly the same way as was pointed out 
in my last paper (‘ Quarterly Journal of Micr. Science, April, 
1881) of Jacobson’s organ of the guinea-pig. We must for 
the present omit to enter into a detailed description of this open- 
ing, since we shall return to it further below; at present we will 
only concern ourselves with Jacobson’s cartilage, and trace this 
backwards all along the organ of Jacohson, of which it forms 
the chief support. 
The next shape of Jacobson’s cartilage after the one shown 
in fig. 3 is one illustrated in fig. 4, that is, the extremities of 
the two labia have joined, and Jacobson’s cartilage forms now 
a complete capsule around the organ of Jacobson, which is 
a complete tube (13, fig. 4). In this shape it resembles 
Jacobson’s cartilage in the guinea-pig in about the anterior half . 
of the organ of Jacobson, as illustrated in fig. 1 of my first paper 
on this subject (‘ Quarterly Journal of Micr, Science,’ January, 
1881). In some sections through this region I notice that the 
median walls of the capsule of Jacobson’s cartilage of the two 
sides are more or less continuous with one another to a very small 
extent in the lower part. But in this shape Jacobson’s cartilage 
does not extend for any considerable distance, any more than was 
the case in the guinea-pig, for in the rabbit it soon changes in 
this manner, that the capsule is discontinuous in the upper wall, 
but slightly directed outwards, so that we again distinguish an 
outer or lateral from an inner or median labium. Owing to this 
discontinuity being established, not in a straight upward, but 
slightly oblique and outward direction, it follows that the median 
Jabium is longer than the lateral one. 
The next change is this: the extremity of the outer labium 
? 
