AND NERVES OF THE TONGUE OF THE FROG AND TOAD. 
145 
papillary structure which must effectually prevent our seeing them in these tissues. 
In my researches on the frog’s tongue, I have never observed any alteration in the 
appearance of the tubules in support of this hypothesis, which 1 am therefore led to 
reject. In searching for the extremities of these nerves, which for brevity I will 
term the tactile nerves, in opposition to the others which are either gustatory or 
muscular, I experience considerable difficulty in detecting them until one or two 
simple tubes are seen, which being followed for some distance, serve as a clue to 
numerous other convolutions around them. By this means a spot which a moment 
before appeared covered with epithelium and destitute of nerves, is seen to be covered 
with abundant nerve-tubes distributed in the way I have mentioned. If such is the 
case with regard to the nearly transparent epithelium and papillae of the frog, how 
much more so must it be the case in the papillae of the skin, where observers have 
hitherto sought them, and where they are obliged to employ chemical agents to in- 
crease the transparency of this membrane ! 
To attain a view of their terminations, we are obliged to flatten the papillae by 
compression. In this state we cannot determine to what height the nerves ascend 
within them. I have repeatedly in vain attempted to trace the nerve in the conical 
papillae, seen in section at the borders of a fragment, while at the same time in an 
adjacent fungiform papilla I have obtained a perfect sight of the gustatory nerves. 
The farthest points to which I have followed them in these circumstances has been 
to their base, where the capillaries and the muscular fibres form a kind of basement 
structure. Here the nerves are found agglomerated together in knots, wherein the 
continuity of the tubules could not be traced. These knots were probably of a gan- 
glionic nature. Over the vessels nerve-tubules of about one-third of the size of 
ordinary nerve-tubes were sometimes seen. 
Nerves of the Fungiform Papillce . — The papillary nerve may be seen at some 
distance before it reaches the pedicel, to form numerous waving incurvations, which 
appear to increase as it approaches it. Near the pedicel we usually perceive a kind 
of knot which contains numerous loops of the nerve. Before it reaches this knot, it 
is found to be composed of separate nerve-tubules, generally not more than five or 
six in number. If not sufficiently distinct, it may be rendered more so by a drop of 
alkali which dissolves the epithelium. In following the nerve to the pedicel, we per- 
ceive that it becomes darker, its fibres more confused, and occasionally with vesicular 
granules interposed between the tubules. When the expanded tongue is seen with 
a low power, the nervous knot at the pedicel is almost invariably detected by its 
dark-grey aspect and numerous loops. After forming this intricate arrangement, 
the nerve-tubules ascend into the interior of the papillae, and expanding, become less 
dark. By the use of the compressorium and the alkali we are enabled to see their 
termination with ease. After nearly attaining the summit of the papillae, we find some 
of the tubules to separate from the main body at an acute angle, proceeding until they 
reach some of the capillary vessels, where each tubule terminates abruptly, most 
MDCCCXLIX. u 
