THE ORGAN OF JACOBSON IN THE RABBIT, 355 
place, when Jacobson’s cartilage becomes changed into a trough- 
shaped capsule with an upper opening, there is seen along its 
outer or lateral labium, and gradually elongating so as to reach up 
to tle upper extremity of this latter, a lamina of bone extending 
from the lateral portion of the intermaxillary bone; this condi- 
tion is accurately illustrated in figures 5—9. It is also noticed 
that this osseous lamina supporting the outer labium of Jacob- 
son’s cartilage increases slightly in thickness towards its upper 
extremity. In the posterior extremity of the organ of Jacobson 
also the inner or median labium of Jacobson’s cartilage receives 
a bony support from the median portion of each intermaxillary 
bone, in the shape of an osseous lamina extending for a relatively 
short distance in the median line separating the Jacobson’s car- 
tilage of the two sides (see fig. 8). But in no place does the 
organ of Jacobson, or rather Jacobson’s cartilage, receive a sup- 
port from the intermaxillary bones to such an extent as is the 
case In the guinea-pig. ha 
In addition to the cartilages described hitherto there exists a 
cartilage in the rabbit which, as far as I can see, is not represented 
in the guinea-pig, viz. a curved or trough-shaped plate of hyaline 
cartilage, the concavity of which coincides with the lower nasal 
furrow; the mucous membrane of this latter forms indeed the lining 
of that trough-shaped cartilage plate. The most anterior point 
where this cartilage is met with is the one depicted in fig. 4; it will 
be seen that Jacobson’s cartilage is a closed capsule and that the 
mucous membrane of the lower nasal furrow is supported by a 
trough-shaped cartilage plate ; on one side the lower nasal furrow 
appears closed as if.to form atube. ‘The fact is, that we have 
here on one side of the section the upper extremity of the Stenson’s 
or Stenonian duct, or the naso-palatine canal, while on the other 
side the communication of this duct with the lower nasal furrow 
is seen widely open. 
Just as in the guinea-pig so also in the rabbit, the Stenonian canals 
open into the nasal furrow, and are not in any way in a direct communica- 
tion with the organ of Jacobson. 
The trough-shaped cartilage plate just named as supporting 
the mucous membrane of the lower nasal furrow is in reality a 
continuation of Stenson’s cartilage, z.e. the cartilage forming the 
support of Stenson’s duct, and for this reason the former may be 
called the Stenson’s or Stenonian cartilage. It extends as far as the 
organ of Jacobson does (see fig. 9) and terminates with Jacobson’s 
cartilage. It is uninterrupted in its whole extension and does not 
alter in shape, size, or thickness, except at its posterior extremity, 
where it suddenly becomes shorter and thinner. 
