THE ORGAN OF JACOBSON IN THE DOG. 307 



and the rabbit, and also the mucous membrane of the nasal 

 septum is richly supplied with the same serous gland. 



The glands are small, and they are present only in small 

 numbers about the region of the upper and lower sulcus ; in 

 tlie former they are larger and more numerous than in the 

 latter. Their ducts open into the upper or lower sulcus 

 respectively ; the lining epithelium is a single layer of 

 columnar cells without cilia, but continuous with the epi- 

 thelium of the lumen of the organ. 



The glands of the upper sulcus can be traced to form a 

 continuity with the glands of the mucous membrane of the 

 nasal septum. 



Only exceptionally are there any glands present in the 

 middle of the lateral wall, and in this case their duct opens 

 straight in the middle of the surface of the lateral wall. 

 This condition obtains especially in the hind portion of the 

 organ, but is only rarely met with in the anterior part. 



The difference in structure of the lateral wall of Jacobson's 

 organ in the rabbit and dog are then considerable, as will 

 be easily seen from a reference to my paper in the Oetober 

 number, 1881, of this Journal. Besides the difference in the 

 shape of Jacobson's cartilage in the two cases, and besides 

 tiie difference in the amount of the serous glands discharging I 

 their secretion into the cavity of the organ of Jacobson, there 

 is this striking difference between the two cases, that in the 

 dog the cavernous tissue, so strongly developed in the lateral 

 wall of the organ in the rabbit and also in the guinea-pig, 

 is altogether absent from the lateral wall of the organ in the 



do?:- 



II. The median wall, (a) The sensory epithelium is a 

 conspicuous part of the median wall. As is the case in the 

 organ of the guinea-pig and rabbit, so also in the dog, the 

 sensory epithelium is well defined from the epithelium of 

 the lateral wall and that lining the upper and lower sulcus. 

 Besides, the sensory epithelium differs in structure from the 

 rest of the epithelium, for here we find the following ele- 

 ments : — (a) A superficial layer of very thin long conical, 

 or spindle-shaped, or cylindrical epithelial cells, each with 

 an oval nucleus ; no cilia are to be seen on the surface ; the ^ 

 cells are longer and thinner than the ciliated cells of the 

 superficial layer of the epithelium of the lateral wall. The 

 individual epithelial cells are possessed of a single or divided 

 or branched process, extending into the deeper layers of the 

 sensory epithelium ; the opposite extremity, i. e. the one 

 reaching the free surface of the epithelium, is either thin 

 and rod-shaped or it spreads out fan-like, and with the free 



