11 
From the number and size of the nerve-fibres constituting 
the bundle in the centre of the papilla, we should infer that 
the finest ramifications resulting from the subdivision of these 
branches would be very numerous, since it has been shown 
that the fine fibres resulting from the subdivision of a single 
dark-bordered fibre in the frog’s bladder, palate, skin, and 
muscle, constitute plexuses or networks which pass over a 
very extended area. The mode of formation of a nerve- 
plexus is represented in PI. Ill, figs. 11 and 14. In these 
beautiful little organs the numerous fibres resulting from the 
subdivision of the dark-bordered fibres are distributed over a 
comparatively small extent of tissue, forming the summit of 
the papilla. Still, we have the same formation of plexuses, 
the constant change in the direction taken by fibres, and the 
same crossing and intercrossing which have been noticed in 
other situations. In fact, the nerve distribution in these 
organs presents the same typical arrangement as is met with 
in other tissues, but it is compressed into a very small space. 
Now r , with regard to the epithelium-like structure upon 
the summit, it has been shown that the nerve-fibres are pro- 
bably continuous with the material lying between the large 
nuclei. In fact, if the interpretation of the appearances 
which I have given be correct, the arrangement may be ex- 
pressed thus : 
The material marked a (PI. I, fig. 2) is a continuation 
of the nervous structure or tissue, while the matter marked b 
bears the same relation to this as the so-called nucleus of a 
nerve bears to its fibre, or that of an epithelial cell to its wall. 
If this be so, the matter which is freely exposed at the very 
summit of the papilla is at least structurally continuous with 
nerve-tissue, if it is not to be regarded as nerve itself. My 
own opinion is that it is just as much nerve-tissue as a fine 
nerve-fibre is nerve-tissue, or the caudate process of a nerve- 
cell is nerve-tissue. The formed matter is produced by the 
large masses of germinal matter which are so very numerous, 
just as the formed matter of a central nerve-cell results from 
changes occurring in its germinal matter. 
It may not be out of place here to consider how the 
elaborate organ connected with the bundle of nerve-fibres of 
the papilla may act during life. As already stated, the free 
surface is uneven, and the arrangement is such that there are 
many elevations projecting, like fibres, by slightly varying 
distances, from the general surfaces. Now, from the intricate 
interlacement of the nerve-fibres in the summit of a papilla, 
as well as at the point between this and the peculiar organ 
ti.Pl. II, fig. 3, b ), it is obvious that a fibre given off from one 
