THE ORGAN OF JACOBSON IN THE DOG. 301 



shown with its thick stratified epithelium and its well-deve- 

 loped and long papillte; at o is the opening of the canal on 

 the surface of the palate ; at p is the mucous membrane 

 of the palate at the side of this opening ; the epithelium is 

 here much thinner and the papillae shorter than on the Pa- 

 pilla. It is seen in figs. 1 and 2 that near the opening or 

 mouth the Stenson's canal enlarges in a sort of sinus, and 

 that it {i.e. the canal) is surrounded on its outer side by a 

 trough-shaped plate of hyaline cartilage, indicated at c of 

 the figures .; this cartilage is Stenson^s .cartilage. As is seen 

 in figs. 5 and 6, the upper part of Stenson's canal becomes 

 frradually constricted off from the rest, and represents then 

 the beginning of the organ of Jacobson, as in fig. 6. At the 

 same time it is seen that Stenson's cartilage undergoes some 

 change in position, the lower part of it disappears, whereas 

 the upper part curves round the upper part of Stenson's 

 canal ; and when this becomes constricted off as the organ 

 of Jacobson, the cartilage forms a curved plate round 

 this latter, so that while the cartilage was previously 

 situated on, and curved round the outer surface of Stenson's 

 canal, it is now situated on, and curved round the median or 

 inner surface of the organ, and consequently is now no more 

 Stenson's but Jacobson's cartilage. Compare figs. 3, 4, 6, 

 and 6. This separation of the organ of Jacobson from the 

 Stenson's canal, as indicated in fig. 6, occurs still on the 

 oral side of the osseous palate ; immediately before, and 

 while traversing this latter the canal of Stenson and the 

 tubes or organs of Jacobson retain exactly the same relative 

 position. And also the cartilage retains its shape and 

 position, i.e. being a curved cartilage plate on the median 

 or inner side of Jacobson's organ (see fig. 7), i.e. Jacobson's 

 cartilage. 



The structure of the different parts is as follows : 

 1. The canal of Stenson. (a) The epithelium lining the 

 canal is throughout stratified. The stratified pavement epi- 

 thelium of the palate, together with its superficial stratum 

 corneum, is continued into the mouth of the canal, but there 

 are no papillse in this part, i.e. the mouth of the canal. Very 

 soon, however, when the canal enlarges, i.e. above the 

 mouth, the stratum corneum of the surface is lost, and the 

 epithelium, although remaining stratified, nevertheless 

 changes its character somewhat, inasmuch as its superficial 

 cells are not much flattened, but are distinctly polyhedral 

 or even cubical cells ; the cells of the middle layers are 

 polyhedral, and those of the deep layers ai-e much elongated 

 in a vertical direction, cylindrical or spindle shaped. The 



