When Man left the water, however,--or what was to develop into Man--he
took very much more ashore with him than a shell. Instead of crawling
ashore at the worm stage, he remained in the water until he evolved
into something like a fish; so that when, after an amphibian
interlude, he finally left it, many "ancient and fish-like"
characters remained in his body to tell the tale. Now, it is among
these piscine characteristics that we find the clue to where Man got
his ears. The chief characteristic of a fish is its apparatus for
breathing the air dissolved in the water. This consists of gills
supported on strong arches, the branchial arches, which in the
Elasmobranch fishes are from five to seven in number and uncovered
with any operculum, or lid. Communicating with these arches, in order
to allow the water which has been taken in at the mouth to pass out at
the gills, an equal number of slits or openings are provided in the
neck. Without these holes in their neck all fishes would instantly
perish, and we may be sure Nature took exceptional care in perfecting
this particular piece of the mechanism. Now it is one of the most
extraordinary facts in natural history that these slits in the fish's
neck are still represented in the neck of Man. Almost the most
prominent feature, indeed, after the head, in every mammalian embryo,
are the four clefts or furrows of the old gill-slits.[1] They are
still known in embryology by no other name--gill-slits--and so
persistent are these characters that children have been known to be
born with them not only externally visible--which is a common
occurrence--but open, through and through, so that fluids taken in at
the mouth could pass through them and trickle out at the neck. This
fact was so astounding as to be for a long time denied. It was thought
that when this happened, the orifice must have been accidentally made
by the probe of the surgeon. But Dr. Sutton has recently met with
actual cases where this has occurred. "I have seen milk," he says,
"issue from such fistulae in individuals who have never been submitted
to sounding."[2]
[1] N. B.--They appear as "clefts," marking not the adult fish, but
the embryo at the corresponding stage.
[2] "Evolution and Disease," p. 81.
In the common case of children born with these vestiges, the old
gill-slits are represented by small openings in the skin on the sides
of the neck and capable of admitting a thin probe. Sometimes the place
where they have been in childhood is marked throughout life by small
round patches of white skin. These relics of the sea, these
apparitions of the Fish, these sudden resurrections, are betrayals of
man's pedigree. Men wonder at mummy-wheat germinating after a thousand
years of dormancy. But here are ancient features bursting into life
after unknown ages, and challenging modern science for a verdict on
their affinities.
When the fish came ashore, its water-breathing apparatus was no longer
of any use to it. At first it had to keep it on, for it took a long
time to perfect the air-breathing apparatus which was to replace it.
But when this was ready the problem was, what to do with the earlier
organ? Nature is exceedingly economical, and could not throw all this
mechanism away. In fact Nature almost never parts with any structure
she has once made. What she does is to change it into something else.
Conversely, Nature seldom makes anything new; her method of creation
is to adapt something old. Now when Nature started out to manufacture
ears, she made them out of the old breathing apparatus. She saw that
if water could pass through a hole in the neck, sound could pass
likewise, and she set to work upon the highest up of the five
gill-slits and slowly elaborated it into a hearing organ.
[Illustration: ADULT SHARK (AFTER CUVIER AND HAECKEL).--FROM "DARWIN AND
AFTER DARWIN."]
There never had been an external ear in the world till this was done,
or any good ear at all. Creatures which live in water do not seem to
use hearing much, and the sound-waves in fishes are simply conveyed
through the walls of the head to the internal ear without any definite
mechanism. But as soon as land-life began, owing to the changed medium
through which sound-waves must now be propagated, a more delicate
instrument was required. And hence one of the first things attended to
was the construction and improvement of the ear.
[Illustration: MARBLE HEAD OF SATYR, IN MUNICH, SHOWING CERVICAL
AURICLES.]
It has long been a growing certainty to Comparative Anatomy that the
external and middle ear in Man are simply a development, an improved
edition, of the first gill-cleft and its surrounding parts. The
tympano-Eustachian passage is the homologue or counterpart of the
spiracle, associated in the shark with the first gill-opening.
Professor His of Leipsic has worked out the whole development in
minute detail, and conclusively demonstrated the mode of origin of the
external ear from the coalescence of six rounded tubercles surrounding
the first branchial cleft at an early period of embryonic life.
Haeckel's account of the process is as follows: "All the essential
parts of the middle ear--the tympanic membrane, tympanic cavity, and
Eustachian tube--develop from the first gill-opening with its
surrounding parts, which in the Primitive Fishes (_Selachii_) remains
throughout life as an open blowhole, situated between the first and
second gill-arches. In the embryos of higher Vertebrates it closes in
the centre, the point of concrescence forming the tympanic membrane.
The remaining outer part of the first gill-opening is the rudiment of
the outer ear-canal. From the inner part originates the tympanic
cavity, and further inward, the Eustachian tube. In connection with
these, the three bonelets of the ear develop from the first two
gill-arches; the hammer and anvil from the first, and the stirrup from
the upper end of the second gill-arch. Finally as regards the external
ear, the ear-shell (_concha auris_), and the outer ear-canal, leading
from the shell to the tympanic membrane--these parts develop in the
simplest way from the skin-covering which borders the outer orifice of
the first gill-opening. At this point the ear-shell rises in the form
of a circular fold of skin, in which cartilage and muscles afterwards
form."[3]
[3] HAECKEL: "Evolution of Man," vol. ii, p. 269.
[Illustration: HEAD OF SATYR IN GROUP OF MARSYAS AND APOLLO, NAPLES
MUSEUM, SHOWING CERVICAL AURICLES.]
Now bearing in mind this account of the origin of ears, an
extraordinary circumstance confronts us. Ears are actually sometimes
found bursting out _in human beings_ half way down the neck, in the
exact position--namely along the line of the anterior border of the
sterno-mastoid muscle--which the gill-slits would occupy if they still
persisted. In some human families where the tendency to retain these
special structures is strong, one member sometimes illustrates the
abnormality by possessing the clefts alone, another has a cervical
ear, while a third has both a cleft and an ear,--all these of course
in addition to the ordinary ears. This cervical auricle has all the
characters of the ordinary ear, "it contains yellow elastic cartilage,
is skin-covered, and has muscle-fibre attached to it."[4]
[4] SUTTON: "Evolution and Disease."
[Illustration: FAUN FROM THE CAPITOLINE MUSEUM, SHOWING CERVICAL
AURICLES.]
Dr. Sutton further calls attention to the fact that on ancient statues
of fauns and satyrs cervical auricles are sometimes found, and he
figures the head of a satyr from the British Museum, carved long
before the days of anatomy, where a sessile ear on the neck is most
distinct. A still better illustration may be seen in the Art Museum at
Boston on a full-sized cast of a faun belonging to the later Greek
period; and there are other examples in the same building. One
interest of these neck-ears in statues is that they are not as a rule
modelled after the human ear but taken from the cervical ear of the
goat, from which the general idea of the faun was derived. This shows
that neck-ears were common on the goats of that period--as they are on
goats to this day--but the sculptor would hardly have had the daring
to introduce this feature in the human subject unless he had been
aware that pathological facts encouraged him. The occurrence of these
ears in goats is no more than one would expect. Indeed one would look
for them not only in Man, but in all the Mammalia, for so far as their
bodies are concerned all the higher animals are near relations.
Observations on vestigial structures in animals are sadly wanting; but
they are certainly found in the horse, pig, sheep, and others.
[Illustration: FORM OF THE EAR IN BABY OUTANG.--FROM "DARWIN AND AFTER
DARWIN"]
That the human ear was not always the squat and degenerate instrument
it is at present may be seen by a critical glance at its structure.
Mr. Darwin records how a celebrated sculptor called his attention to a
little peculiarity in the external ear, which he had often noticed
both in men and women. "The peculiarity consists in a little blunt
point, projecting from the inwardly folded margin or helix. When
present, it is developed at birth, and according to Professor Ludwig
Meyer, more frequently in man than in woman. The helix obviously
consists of the extreme margin of the ear folded inwards; and the
folding appears to be in some manner connected with the whole external
ear being permanently pressed backwards. In many monkeys who do not
stand high in the order, as baboons and some species of macacus, the
upper portion of the ear is slightly pointed, and the margin is not at
all folded inwards; but if the margin were to be thus folded, a slight
point would necessarily project towards the centre."[5]
[5] "Descent of Man," p. 15.
Here then, in this discovery of the lost tip of the ancestral ear, is
further and visible advertisement of man's Descent, a surviving symbol
of the stirring times and dangerous days of his animal youth. It is
difficult to imagine any other theory than that of Descent which could
account for all these facts. That evolution should leave such clues
lying about is at least an instance of its candor.
[Illustration: HORNED SHEEP AND GOAT WITH CERVICAL AURICLES.--FROM
"EVOLUTION AND DISEASE," J. BLAND-SUTTON.]
But this does not exhaust the betrayals of this most confiding organ.
If we turn from the outward ear to the muscular apparatus for working
it, fresh traces of its animal career are brought to light. The
erection of the ear, in order to catch sound better, is a power
possessed by almost all mammals, and the attached muscles are large
and greatly developed in all but domesticated forms. This same
apparatus, though he makes no use of it whatever, is still attached to
the ears of Man. It is so long since he relied on the warnings of
hearing, that by a well-known law the muscles have fallen into disuse
and atrophied. In many cases, however, the power of twitching the ear
is not wholly lost, and every school-boy can point to some one in his
class who retains the capacity and is apt to revive it in irrelevant
circumstances.
One might run over all the other organs of the human body and show
their affinities with animal structures and an animal past. The
twitching of the ear, for instance, suggests another obsolete or
obsolescent power--the power, or rather the set of powers, for
twitching the skin, especially the skin of the scalp and forehead
by which we raise the eyebrows. Sub-cutaneous muscles for shaking
off flies from the skin, or for erecting the hair of the scalp,
are common among quadrupeds, and these are represented in the human
subject by the still functioning muscles of the forehead, and
occasionally of the head itself. Everyone has met persons who possess
the power of moving the whole scalp to and fro, and the muscular
apparatus for effecting it is identical with what is normally
found in some of the Quadrumana.
Another typical vestigial structure is the _plica semi-lunaris_, the
remnant of the nictitating membrane characteristic of nearly the whole
vertebrate sub-kingdom. This membrane is a semi-transparent curtain
which can be drawn rapidly across the external surface of the eye for
the purpose of sweeping it clean. In birds it is extremely common, but
it also exists in fish, mammals, and all the other vertebrates. Where
it is not found of any functional value it is almost always
represented by vestiges of some kind. In Man all that is left of it is
a little piece of the curtain draped at the side of the eye.
When one passes from the head to the other extremity of the human
body one comes upon a somewhat unexpected but very pronounced
characteristic--the relic of the tail, and not only of the tail, but
of muscles for wagging it. Everyone who first sees a human skeleton
is amazed at this discovery. At the end of the vertebral column,
curling faintly outward in suggestive fashion, are three, four, and
occasionally five vertebrae forming the coccyx, a true rudimentary
tail. In the adult this is always concealed beneath the skin, but
in the embryo, both in man and ape, at an early stage it is much
longer than the limbs. What is decisive as to its true nature,
however, is that even in the embryo of man the muscles for wagging
it are still found. In the grown-up human being these muscles are
represented by bands of fibrous tissue, but cases are known where
the actual muscles persist through life. That a distinct external
tail should not be still found in Man may seem disappointing to the
evolutionist. But the want of a tail argues more for the theory of
Evolution than its presence would have done. It would have been
contrary to the Theory of Descent had he possessed a longer tail. For
all the anthropoids most allied to Man have long since also parted
with theirs.
It was formerly held that the entire animal creation had contributed
something to the anatomy of Man, that as Serres expressed it "Human
Organogenesis is a condensed Comparative Anatomy." But though Man has
not such a monopoly of the past as is here inferred--other types
having here and there emerged and developed along lines of their
own--it is certain that the materials for his body have been brought
together from an unknown multitude of lowlier forms of life.
[Illustration: EAR OF BARBARY APE, CHIMPANZEE, AND MAN, SHOWING VESTIGIAL
CHARACTERS OF THE HUMAN EAR.--FROM "DARWIN AND AFTER DARWIN."]
Those who know the Cathedral of St. Mark's will remember how this
noblest of the Stones of Venice owes its greatness to the patient
hands of centuries and centuries of workers, how every quarter of the
globe has been spoiled of its treasures to dignify this single shrine.
But he who ponders over the more ancient temple of the human body will
find imagination fail him as he tries to think from what remote and
mingled sources, from what lands, seas, climates, atmospheres, its
various parts have been called together, and by what innumerable
contributory creatures, swimming, creeping, flying, climbing, each of
its several members was wrought and perfected. What ancient chisel
first sculptured the rounded columns of the limbs? What dead hands
built the cupola of the brain, and from what older ruins were the
scattered pieces of its mosaic-work brought? Who fixed the windows in
its upper walls? What forgotten looms wove its tapestries and
draperies? What winds and weathers wrought the strength into its
buttresses? What ocean-beds and forest glades worked up the colors?
What Love and Terror and Night called forth the Music? And what Life
and Death and Pain and Struggle put all together in the noiseless
workshop of the past and removed each worker silently when its task
was done? How these things came to be Biology is one long record. The
architects and builders of this mighty temple are not anonymous. Their
names, and the work they did, are graven forever on the walls and
arches of the Human Embryo. For this is a volume of that Book in which
Man's members were written, which in continuance were fashioned, when
as yet there was none of them.