MINUTE ANATOMY OE THE PAPILLAE OE THE FROG’S TONGUE. 
449 
of ending of nerves in this situation ; but it is most certain that the fibres do divide and 
subdivide into finer and much more transparent fibres at this point, and that these again 
divide and subdivide and form an elaborate plexus in the summit of the papilla, which 
has not been before described. 
By reference to the figure, the arrangement, which is not easily described with 
accuracy, will be at once understood, so that a minute description of it would be super- 
fluous. 
Above the plexus c (Plate XXI. fig. 3), and below the epithelium-like organ at the 
summit of the papilla (a), is a layer ( b ) which appears to be composed of granular matter. 
In my most perfect specimens, however, this “granular layer,” when examined by very 
high powers under the influence of a good light, is seen to consist of a plexus of 
extremely fine fibres which interlace with one another in every direction, but which 
pass from the plexus above to the epithelium-like nervous (1) organ upon the summit 
of the papilla (Plate XXI. fig. 2). I believe this granular appearance to result from 
the extreme delicacy and fineness of the nerve-fibres at this part of their course. In 
like manner the “ granular matter” seen in the grey matter of the cerebral convolutions 
and that of the retina, results mainly from the breaking down of very fine and delicate 
nerve-fibres, which undergo disintegration very soon after death, unless they are sub- 
jected to special methods of preparation. 
Of the existence of the elaborate network of nerve-fibres with the large nuclei, repre- 
sented in Plate XXI. fig. 3 c , there can be no question whatever ; but there may be 
some difference of opinion regarding the exact relation of the very fine nerve-fibres at 
the summit of the papilla, to the peculiar cells which surmount it, and the nature 
of the granular matter just described. However, there are but two possible arrange- 
ments : — 
1. That the nerves form a network of exceedingly fine fibres upon the summit of the 
papilla, upon which the bases of the epithelium-like cells impinge. 
2. That the very fine nerve-fibres are really continuous with the peculiar and epithe- 
lium-like cells ; in which case these bodies must be regarded as part of the nervous 
apparatus. 
There seems to me to be so much strong evidence in favour of the last view, that 1 
venture to express a decided opinion that this is the truth. In many specimens I have 
seen, and most distinctly, the delicate network of fibres represented in Plate XXI. 
fig. 3 continuous with the fine nerve-fibres in the summit of the papilla, and I have 
demonstrated the continuity of these fine fibres with the matter of which the outer part 
of these peculiar cells consists (Plate XXI. figs. 2, 3, 6). I have also seen what I 
consider to be nerve-fibres in the intervals between some of these cells (Plate XXI. 
fig. 7). Upon the whole I am justified in the inference that there is a structural 
continuity between the matter which intervenes between the masses of germinal matter 
at the summit of the papilla and the nerve-fibres in its axis, and I consider that an 
impression produced upon the surface of these peculiar cells may be conducted by con- 
