Freiburger historische Bestände - digital

1

c.

THE PROBOSCIS.

The right and the left upper lips of the Dog, towards their
anterior ends, become lower and, in the middle line, before the
incisors, — where they unite, — form a thick vertical fold (PI. 17,
fig. 5), the mucous side of which is a somewhat oblique plane,
separated from the hard palate, first by a low gingiva and then
by the incisors. The outer face of the median part of the upper
lips has a vertical direction; dorsad it is continued into that part
of the skin which surrounds the nostrils and which is partially
lying in the same plane. The nostrils are round openings directed
forwards and continued by a slit laterally. The skin surrounding
the nostrils is hairless and areolated; only below the
slit mentioned the skin is hairy. The outer face also of the median
part of the upper lip is hairy; only a narrow median furrow
running from between the nostrils unto the margin of the
lip is bare. On the inside of the lip there is no median furrow,
but a median projecting fold (frenulum).

The said median part of the upper lip, and the region lying
above it, surrounding the nostrils, is the snout proper. Into it
extends the anterior part of the cartilaginous nose.

The extent of the hairless portion of the skin of the snout is
exceedingly different in various Mammals. Sometimes it extends
farther than in the Dog; e. g. in Procyon lotor the lower margin
of the slitlike portion of the nostrils also is bare; sometimes
the upper lip, below the nares, is endowed with only a very few
hairs (Tragulus etc.). In others the case is quite contrary: the
hairless parts being reduced; e. g. in the Goat and the Horse the
nostrils are entirely surrounded with hairy skin, which extends
also into the anterior part of the nasal cavities; only the median
furrow on the upper lip is still bare in the Goat. Other forms,
e. g. the Red deer, take up an intermediate position.

The median furrow on the upper lip is not always present;
it may be quite levelled. But it may also be continued on
the mucous side of the lip (Lemur, Red deer). And the furrow
may be so deep, that the upper lip in the median line is separated
into two halves, as is the case in many Rodents.

In Mammals in which the median incisors are wanting, the
mucous side of the median portion of the upper lip may be a
direct continuation of the hard palate, the perpendicular or oblique
direction of this side of the lip being modified into a horizontal.
Such is the case in Tragulus (PI. 17, fig. 9) and Lemur.

Another alteration in the relative position of the various sections
of the surface of the region in question is found in Man
(PI. 17, fig. 12). Here the direction of the mucous and external side
of the median portion of the upper lip is the same as in the Dog
and most other Mammals. But the area surrounding the nostrils
has altered its position from a vertical into a horizontal one, meeting

in an angle the outer face of the upper lip, which in the Dog,
and others, lies in the continuation thereof.

In the Mammals (PI. 17, fig. 7,10 etc.), in which the snout is
elongated into a longer or shorter proboscis projecting beyond
the lower lip: several Insectivora, Sus, Nasua etc. (the Tapir and
the Elephant we for the present set aside), it is the dorsal part
of the snout, unto the area round the nostrils, which in the first
place has become elongated. The area round the nostrils has not
generally been substantially altered, and has retained its original
vertical position on the end of the snout. The margin of the lip
has retained its original position, and the outer face of the median
portion of the upper lip has therefore, as a sequence of the
prolongation of the dorsal side of the snout, been forced to change
its vertical position into a horizontal one. The ventral side of the
proboscis is thus the homologue of the outer face of the median
part of the upper lip lying between the margin of the lip and the
area round the nostrils. With this area it is connected by an angle,
which is inverse to the angle between these two sections of the
surface in Man (comp. fig. 7 and 12, PI. 17). — The Badger (PI. 17,
fig. 6) forms an interesting connecting link between an ordinary
Mammal, as the Dog, and Mammals with a proboscis, the outer
face of the median portion of the upper lip in the Badger being
not vertical as in the Dog, nor horizontal as in the proboscidi-
ferous, but oblique.

As to the mucous side of the median portion of the upper
lip. It has, in Mammals with a proboscis, sometimes remained
as in the Dog. Such is the case in Nasua (fig. 7), and also in
Myogale and Talpa (fig. 10), in which latter the margin of the lip
projects as a low thin brim on the border of the outer and the
inner face of the upper lip; also in the Swine the same is the
case. In others the mucous side of the lip has also taken a horizontal
position, lying in the direct continuation of the outer
side of the lip (viz. the lower side of the proboscis) and being
also posteriorly directly continued into the hard palate, there
being in the same forms a toothless space in front. Such is the
case in Erinaceus, Macroscelides (fig. 8) and Centetes.

The median furrow, which in the Dog and others is present
on the outer — and sometimes also on the mucous — face of
the upper lip, may also be present in the corresponding place in
proboscidiferous Mammals. It is very marked in Erinaceus, where
it is continued into the hard palate and is laterally bounded by
a bare raised border. In Macroscelides the furrow is very deep,
growing broader proximad and being continued unto the mouth.
In Centetes, whose proboscis is very short, the furrow is continued
on the mucous side of the lip (which is in Centetes sharply