THE ORGAN OF JACOBSON IN THE RABBIT. 565 
it appears limited by a membranous structure, similar to the 
limiting membrane of v. Brun in the olfactory organ. 
The thickness of the layer containing the oval nuclei of these 
epithelial cells is between 0°027 and 0:028 mm. 
The size of these nuclei is 0°0054 by 0°0072, or 0°:0036 by 
0°009 mm. 
Underneath the epithelial cells, or rather underneath the nuclei 
indicative of them, follows the deep stratum or the stratum of the 
sensory cells. These cells are spindle-shaped or multipolar, 
possessed of a cell body of clear, granular-looking substance, 
and including a spherical nucleus, the size of which is about 
00072 mm. ; being spherical these nuclei are therefore larger 
than the oval nuclei of the ‘epithelial cells.” Besides, 
the nuclei of the sensory cells are more transparent and less 
stained in preparations stained with hematoxylin, and they 
include a beautiful uniform network, or in some cases a convolu- 
tion of fibrils. : 
In a preparation hardened with spirit and stained with log- 
wood the contrast between the two strata, z. ¢. the stratum of 
the epithelial cells with deeply-stained homogeneous nuclei, and 
the stratum of the sensory cells, with the large clear spherical 
nuclei, is very great indeed, and no one looking at such a speci- 
men can for a moment fail to see it. The number of sensory 
cells, or their nuclei indicative of them, differs in different parts ; 
it is greatest in about the middle of the median wall, and de- 
creases towards the upper and lower sulcus. The greatest thick- 
ness of the stratum of sensory cells is about 0°18 mm., and the 
greatest number of nuclei, from the superficial stratum to 
the subepithelial layer, in a vertical direction, is about eight 
or ten. 
The boundary of the sensory epithelium towards the sub- 
epithelial mucosa is not well defined, the sensory cells Jdeing 
prolonged singly or in small groups into the mucosa. This fact 
does not come out so well in spirit preparations, but is distinct 
in specimens prepared in Miiller’s fluid. In these latter the 
deepest sensory cells, and especially those that extend into the 
mucosa, appear larger in the amount of the cell protoplasm than 
the more superficially situated sensory cells. 
Everywhere the cell body is very distinct, owing to its rela- 
tively large size, and when isolated appears, as in the guinea- 
pig’s organ, spindle-shaped or multipolar. The processes, like 
those of the sensory cells in the olfactory nasal membrane, may 
be distinguished as an outer process, extending between the 
“epithelial cells” to the surface, and one or more inner ones 
passing downwards, 7.¢. into the depth towards the mucosa. 
I have described this in my former paper in connection with 
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