308 DR. E. KLEIN. 



margin of this enlargement forms part of the general surface. 

 There is generally noticeable on the free surface a cuticular, 

 sharply-defined boundary layer, similar to the outer limiting 

 membrane of v. Brun of the olfactory organ. The same 

 layer was described also in the organ of the rabbit. The 

 nuclei of the superficial epithelial cells of the sensory epi- 

 thelium are not disposed in a single plane, but the individual 

 epithelial cells possessing their nucleus at variable heights 

 it follows that, viewing the layer of epithelial cells as a 

 whole, we find their nuclei disposed in two or three planes. 

 In a vertical section through the epithelium, such as is re- 

 presented in fig. 15, this point is well shown. In such sec- 

 tions stained with lofjwood or anilin dyes the contrast 

 between these epithelial cells and the cells below them is 

 very marked, just as was the case in the organ of the rabbit; 

 the epithelial cells, by their deeply-stained nuclei, differ 

 conspicuously from the layer of clear nuclei beneath. (j3) 

 Underneath this stratum of epithelial cells is a stratum of 

 sensory cells. In the guinea-pig and rabbit I have shown 

 that this stratum consists of several layers of sensory cells, 

 but in the dog there exists, as a rule, only a single, or at 

 most in some places a double, layer of these cells. In fig. 16 

 these cells are accurately represented ; they appear large 

 ganglionic cells, each possessirig a clear, relatively large, 

 more or less spherical nucleus. Each of these nuclei con- 

 tains, within a definite limiting membrane, a well-developed 

 uniform reticulum with one or two nucleoli. 



The substance of these sensory cells is chiefly accumulated 

 on the side of the nucleus nearest to the epithelial cells, i. e. 

 directed toward the free surface, and it extends either in the 

 shape of a single or divided thinner or thicker process up 

 to the free surface. This is the outer process ; but on the 

 opposite pole there is also one or more processes directed 

 downwards, i. e. towards the depth ; these are the inner pro- 

 cesses. They are much finer, and, as is obvious from 

 the inspection of fig. 15, much shorter than the outer 

 processes. 



(7) Underneath these sensory cells is a limiting layer of 

 small cells, which in specimens hardened in chromic acid 

 appear more or less branched and connected with one 

 another ; their nuclei are spherical and smaller than the 

 nuclei of the sensory cells ; some of these deep cells appear 

 conical, possessing a basis with which they rest on the sub- 

 epithelial membrane, and their apex process is directed in 

 the opposite direction between the sensory and superficial 

 epithelial cells. From this it must be clear that this deep 



