560 DR. E. KLEIN. 
Balogh! says that in the sheep’s organ there exists a “ gland- 
projection” (Driisenwulst) in the mucous membrane of the organ 
of Jacobson, which extends from the upper and outer parts of the 
mucous membrane into the lumen of the organ of Jacobson. 
The bourrelet of Gratiolet and the Driisenwulst of Balogh are 
evidently the same thing, but they differ from the glandfold of 
the middle of the lateral wall as described by me of the rabbit. 
In the guinea-pig there is nothing of the kind, as I have pointed 
out in my former paper. 
In the posterior position of the organ of Jacobson we find 
the following disposition of the several layers :—The median wall 
in its sensory epithelium, and its numerous plexuses of olfactory 
nerve bundles remains unaltered, so does the epithelium of the 
lateral wall, the subepithelial layer, the glandfold, and the elastic 
layer. The cavernous layer, however, becomes greatly increased 
in thickness and extent, encroaching considerably on the lower 
and upper wall; hence the glands opening into the upper suleus 
appear very greatly diminished in numbers. The same is the 
case with the glands opening into the lower sulcus ; these sooner 
or Jater cease altogether. 
At the very extremity of the organ of Jacobson we find the lumen 
reduced to a minute opening; in the median wall we still find a 
trace of the sensory epithelium, but soon this also disappears, 
the lumen becomes circular in transverse section, and the epithe- 
lium is altogether made up of columnar cells. In the posterior 
extremity of Jacobson’s organ the lumen and the lining epithe- 
lium in so far alter their position as they are now close to the 
median labium of Jacobson’s cartilage, and they shift also a 
little more in a downward direction (see figs. 8 and 9). 
A plexus of thin olfactory bundles is still to be recognised in 
the upper part of the median wall, but this latter is greatly 
reduced in thickness. The glands opening into the upper sulcus 
reach lower down than before. 
Of a glandfold in the lateral wall, or of a subepithelial layer, 
nothing is left; the lateral and lower wall are occupied by the 
cavernous tissue, which possesses a considerable thickness, and in 
which the bundles of non-striped muscular cells, running in 
all directions, still form a conspicuous feature. 
We see, then, that in all repects the organ of Jacobson of the 
rabbit differs materially from that of the guinea-pig; the shape 
and size of Jacobson’s cartilage, the disposition of the several 
structures in the median and lateral wall, are quite different 
in the two cases. 
Before describing the minute structure of the different parts 
' Lc, p. 457, 
