306 DR. E. KLEIN. 



wall. Just as was the case in the Jacohson's organ of 

 the guinea-pig and rabbit, so also in the dog, the epi- 

 thelium lining the median wall is supplied with olfactory 

 nerve-branches, and contains their terminations in the shape 

 of peculiar large cells. We shall therefore consider the 

 epithelium lining the median wall as the sensory epithelium. 

 The shape of the lumen of the organ in transverse section 

 being oval, we shall call the upper part the upper sulcus, 

 the lower part the lower sulcus. The whole extent of the 

 lateral wall of the organ including the upper and lower 

 sulcus is distinct and different in structure from the rest 

 of the wall of the organ. The former will be understood 

 to represent the lateral wall in its broader sense, the latter 

 the median wall proper. 



I. The lateral wall. The epithelium lining this wall on 

 the inner free surface is columnar epithelium of exactly the 

 same nature and thickness as the one covering the surface of 

 the mucous membrane of the nasal septum and the nasal fur- 

 row, viz. it is composed of three different kinds of cells : (a) a 

 superficial layer of conical or cylindrical cells, with a bundle 

 of fine cilia on tVie free surface; then (b) a layer of spindle- 

 shaped cells pushed in between the extremities of the first- 

 named cells ; and (c) a deep layer of cells more or less 

 conical, but with their base resting on the subepithelial 

 membrane. In some sections I have met with goblet cells 

 amongst the superficial ciliated epithelial cells. The thick- 

 ness of the epithelium is about 048 to 0'072 mm., exclu- 

 sive of the cilia, which are about 0*006 mm. in length. 



Underneath the epithelium is a dense fibrous membrane, 

 containing numerous lymphoid corpuscles; this infiltration 

 with lymph-cells is more pronounced in the most anterior 

 portions of the organ than further behind. 



A large number of fine elastic fibrils, running longitudi- 

 nally, are met with in the subepithelial membrane. Partly 

 within this, but especially between it and the fibrous 

 bands mentioned above as separating the lateral wall from 

 the mucous membrane of the nasal septum, are numerous 

 vessels, most of them running parallel with the long axis of 

 the organ. Some of these are arteries, but the majority are 

 venous vessels, and they form a plexus. There appears in 

 this respect no difference between the lateral wall of the 

 organ and the mucous membrane covering the free surface 

 of the nasal septum, which is also richly supplied with a plexus 

 of small veins. 



All glands of the organ of Jacobson are serous glands, of 

 exactly the same nature as in the organ of the guinea-pig 



