THE ORGAN OF JACOBSON IN THE DOG. 305 



loose fibrous texture containing numerous large blond- 

 vessels, arteries, and especially veins, running parallel v/ith 

 the long axis of the organ. In an upward and downward 

 direction we meet with small short glands, opening with 

 their ducts into the lumen of Jacobson^s organ. The glands 

 are composed of a few acini, and these are in structure 

 serous glands of exactly the same nature as those described 

 of Jacobson's organ in the guinea-pig and rabbit. 



In the median wall I can trace here and there a branch 

 of olfactory nerve-fibres. The organ' having entered the 

 nasal septum is at first lined with the same stratified 

 pavement epithelium as before, about 0'0864 mm. in thick- 

 ness ; the subepithelial membrane is much infiltrated with 

 lymphoid cells, especially in its lower part. In the median 

 ■wall we find amongst the numerous large blood-vessels 

 a few branches of olfactory nerves running in a longitudinal 

 direction. The serous glands are met with in the same 

 position as before. We now find a distinct layer of fibrous 

 bands, by which the lateral wall of Jacobson's organ be- 

 comes differentiated from the mucous membrane liningr th'^ 

 surface of the nasal septum in this region. If we imagine 

 in fig. 8 fibrous bands of the perichondrium of Jacobson's 

 cartilage passing from the lateral aspect of the extremity of 

 the ascending to the lateral aspect of the extremity of the 

 horizontal labium, we have a coriect idea of the position of 

 these structures. So that these bands separating the lateral 

 wall of Jacobson's orijan from the outside membrane would 

 have the position of a chorda to the arch represented by 

 the hook-shaped cartilage of Jacobson (see fig. 8). 



And throughout the rest of Jacobson's organ its lateral 

 wall is bounded on its outside in this same manner (see figs. 

 9, 10, 14, and 15). 



But very soon after its entrance into the nasal septum 

 the epithelium of the organ of Jacobson changes its charac- 

 ter. As long as its lumen is circular in transverse section 

 its epithelium is stratified pavement epithelium, but the 

 lumen becoming triangular, and then oblong, the epithelium 

 changes into columnar epithelium. 



This change does not take ])lace simultaneously in the two 

 sides, for while in the organ of one side the whole lining 

 epithelium may be found to be columnar, that of the organ 

 of the other side is still stratified pavement epithelium in 

 the upper and lower part of the wall. 



As soon as the lumen of the organ in transverse section 

 is kidney shaped the epithelium all round is columnar ; that 

 of the median wall is different from that lining the lateral 



