jaw, but its edges are free to a little way behind the angle of the mouth, and thus must
have considerable mobility. In young specimens, 54 inches long, it is traversed by
a raphe which is nearly co-extensive with the free margins, but directed from the
mesial line at the tip to the right side. There is no trace of a foramen csecum or
of circumvallate papillae; the tongue being remarkably smooth, only a few minute
fungiform papillae occurring' on its sides, some distance beyond the angle of the
mouth. In its free portion it is thickly clad with filiform papillae. Below the free
margin, immediately behind the tip, there are small glands which open by four
orifices, generally arranged in a linear series with an azygos orifice above them.
Behind the posterior half of the free border of the tongue and below it, there is a
longitudinal row of large patulous orifices, generally three in number, with two or
three more forming an arch above them. They increase in size from before backwards,
the most posterior being divided by a vertical pillar into two openings. The
orifices lead into sacs or recesses in the mucous membrane, into which one or more
glands appear to open. In close connection with them, and above and behind them
on the side of the free border of the tongue, there occurs a large patch of glandular
orifices of various sizes, some of the more anterior openings being more or-less
surrounded by free folds of the mucous membrane, so that the surface appears rough
and the orifices to be protected by valves. These orifices do not occur further back
than the free margin, and are restricted always to the same spot. The lingual
racemose glands are especially numerous on the root and sides of the tongue, and
each gland appears to open by a distinct orifice, but the glands are not so long as in
Orcella, although they have the same structure. In the adult, the root of the tongue
is frequently corrugated, the corrugations simulating circumvallate papillae, but in
the young, as already stated, it is quite smooth. In the adult also the raphe cannot
be distinguished.
Minute structure o f its Papilla.—The filiform papillae of the tongue microscopically
manifest two distinct characters, each having a special distribution. On
the front they are generally much more numerous than on the back part of the
tongue, and on the former they are fully three times as large as on the latter locality.
These anterior papillae are more or less conical in form, but some are much
broader and stouter than others, and their distinguishing feature is the division of
their summits, and occasionally of their sides, into short non-divergent processes.'
These are very minute, and require a high power to demonstrate them satisfactorily.
Some of them are almost vesicular, and others are oblong and pointed at their free
ends, but all are short and very obscure. The papillae clothing the back part of the
tongue, or that portion on which the majority of the mucous glands open, are very
minute flagilliform processes, situated generally on conical bases, while some are
essentially whip-like, without any basal enlargement.
Racemose mucous glands.—Some of the orifices of those on the dorsum of the
tongue have a pyriform body visible to the naked eye, projecting outwards from
one side of the external termination of the duct. The base of this body is directed
outwards, and its apex is prolonged downwards into the duct for a short way as a
portion of its structure, which is quite distinct from that of the neighbouring
substance of the tongue or of the papillae, in that it has a cellulo-granular or
glandular character. Projecting from the base there is what appears to me to be
an orifice. If this is a glandular structure with an excretory duct, the position
which it occupies as a kind of valve at the orifice of the excretory duct of the highly
complex mucous gland, would render it probable that the two glands are intimately
related to each other. The valvular gland, while performing its special functions in
the economy of the oral cavity, may fulfil a secondary function, by closing the
mucous gland, the secretion of which, it may be important, should not be excreted
along with that of its plug.
Palate.—This presents two furrows internal to, and parallel with, the upper
lips, and into which the lower lips are received when the mouth is closed. The
anterior portion of these furrows is marked by five deep pit-like impressions corresponding
to the five posterior teeth of the lower jaw. I t would thus appear that the
surfaces of the mouth are in very close apposition—a circumstance which is also
verified by the fact that the tip of the tongue is generally marked by the impression
of the two 'most posterior teeth of the upper jaw, and the postsymphysial space
anterior to it -is also marked by the impress of the tèeth. The teeth of the two lines
are not opposite to each other owing doubtless to the asymmetry of the skull, and as
the linfts are posteriorly divergent and approach each other at the front part of the
palate, they are alternate in that region, and immediately external to them are the pits
for the teeth of the lower jaw. There are seven teeth on the left and six on the
right side. The palatal surface posterior to the teeth is slightly convex, but perfectly
smooth. In this same individual, two orifices occur in the palate 6'50 inches posterior
to the first tooth above, in the middle line, half an inch behind the posterior border of
the pterygoids. These mucous crypts are placed transversely, and are separated from
each other by an interval of about 0-25 inch. They are longitudinally oval orifices,
0-l inch long, and each leads into a crypt in the mucous- membrane, into which
small mucous glands open. These orifices I have been unable to detect in an
adult. The palate anterior to them and between and posterior to them, is nearly
devoid of racemose glands, but these structures are numerous on the margin of
the posterior portion of the palate and on the fauces. The soft palate is T75
inch long in the individual under consideration (54 inches), and its posterior
margin is sharp without any indications of an uvula, anterior or posterior pillars, or
tonsils.
Dentition and changes occurring with age.—Sir Everard Home* remarks that
the changes' that take place in the form of the teeth as they wear away from long
use are more remarkable than in most other teeth, for the perfect tooth has a tolerably
sharp enamelled point, while the half-grown tooth has a concave, blunted cutting
edge.
These changes in the form of the free ends of the teeth are also associated with
a remarkable increase in the size of the teeth. In a young specimen differing in no
1 Phil. Trans. 1818, vol. 118, p. 418, plate xx.