THE PLANTAR ARCH.
The principle of Lyell cannot be applied to this section of my
subject for it is unique in the animal world. There is here a simple
compilation of facts such as the medical schoolboy is supposed to know,
and only requires for its setting forth the valuable expert knowledge
of our predecessors in anatomy. It is indeed a pedestrian chapter.
Man alone possesses this mark of a high lineage, and it adds point to
Shakespeare’s description of man as “paragon of animals,” and Huxley’s
“a superb animal, head of the sentient world.” For winning this
integral part of a perfect walking-foot man must stoop to conquer; he
must descend from the trees in order that he may have life and liberty;
whether he bears the ancient surname of Tarsius or the more honoured
one of Pithecus matters not. Names had not in those early times usurped
that tyranny over man’s mind which they have done among his modern
descendants. He came into that terrestrial kingdom which was to be
his own with many a limitation, but with the promise and potency of
an unexampled evolution, when he assumed more fully the erect posture
and saw that his inheritance was very good. Neither then nor since has
he ever reached the fleetness of foot of the Thibetan wild ass, the
astonishing sense of smell of the dog or horse, the keen sight of the
hawk, or the climbing power of that simian family upon whom he turned
his back as on a poor relation. He became _par excellence_ the walking
biped of earth, as, even with greater value to his mastery of the
world he learned to talk in articulate language. A walking animal and
a talking animal, with vast stretches of time for training these new
powers of his, he became modified into the variegated human stocks,
black, yellow and white, that now inhabit the earth.
A Crumbling Arch.
A digression, I hope, will be pardoned here before the value and beauty
of the plantar arch and its mode of forging are described, and it is
possible the latter may add some force to the former. Scientific (or,
must I say?) semi-scientific writings are not concerned with the
snobbishness of much of the pride of birth which still survives among
us. But I would indeed think myself to be doing “my bit” if I could
induce the present generation of young women and men to think highly
of their plantar arches, nobler evidence of a “good” family than soft
fair skin, taper fingers, Grecian nose, slender waist or that hair of
which the decaying line of the long-haired kings of old France were
too proud. For one reason or another, probably analogous to those for
which he has lost so much the vigour of his hair of the scalp, or his
dwindling wisdom-teeth and shrinking little toes, in other words,
racial degeneration, modern man seems to be losing his plantar arch.
For about three years I have made careful but saddening study of the
ankles and feet of young women, and have embodied it in a variety
of journals. This study has included about two thousand examples in
young women of incipient or advanced flat-footedness as revealed,
nay, flaunted before us in our towns and villages. This revelation
has been offered by women’s shortened skirt, so that one can now note
for oneself the ugly and disabling ankles and feet in the streets of
any town, without the complicated business of a surgical examination.
Such an examination, as it happens, and as it is usually undertaken,
serves only to show a moderately advanced degree of this deformity,
indeed, just so much as induces a patient to go to a doctor for relief
of pain or obvious deformity. This is wholly insufficient for the study
of a defect which in the various degrees of its development affects
nearly 90 per cent. of all youngish women so far observed and noted.
The doctors may--or may not--cure this evil, but they are not likely
to find time even to discover during their strenuous lives, the great
spread of this physical defect. But the merciful ukases of fashion,
from Paris or elsewhere, and the obvious benefits, for once, of a
fashion, are so powerful that the short skirt has remained with us for
several years past and does not seem likely to go. I can only hope it
will last until women who lead their sex in these days become ashamed
of the feet of their sisters and their own, and make a forcible attack
upon the Health Minister or Minister of Education, or both, so that
systematic foot-drill in all elementary schools may be established.
No other means than this, added to improved general health, can be
conceived as able to correct so widely spread a deformity. I do not
desire to be considered as making an attack on the bodily charms of
women, for whose multifarious attractions I yield to none in sincere
regard. But here is the revelation, here are the cases walking
unashamed before us, and if the skirts _should_ lengthen again and
cruelly hide up the evil, no one will be induced again to take up the
unpopular attitude of saying that nearly all young women have feet that
are deformed and ugly and, therefore, more or less inefficient. There
is, alas! only too much reason to know that the evil is great among the
better class, even of boys, for in 1919 Captain Coote said publicly at
a Schoolmasters’ Conference that fully 30 per cent. of the new boys
entering leading public schools had flat-foot, and Captain Coote, the
highest exponent of physical training in the Navy, knows a flat-foot
when he sees it. The measures here suggested in connection with the
feet of women have the great merit that from them boys and girls will
alike benefit.
Non-Arboreal Man.
Many problems faced non-arboreal man as he descended from the trees
to claim his suzerainty and place of toil. Not least among them was
the question of methods of protection against the terrible creatures
among which he was to live. Their production must needs be slow, and
for him to meet by “direct action” with weapons invented _ad hoc_
the fierce large carnivora and clumsy but dangerous dinosaurs would
have proved highly dangerous. Too long had they been in possession
of his Canaan, and he could not cross his Jordan, walk seven times
round their Jericho, blowing with trumpets of rams’ horns, and on the
seventh day march in and “consolidate his position.” He had first to
do what his descendants have always been bound to do; he had to learn
to walk terrestrially long before he could think and live imperially.
Sufficient for him was the evil of his day, and, as an old arboreal
denizen he had much to learn and not a little to unlearn; and we know
from the prehistoric pictures of his own doings and trophies, that he
did in course of ages learn to walk, run and jump with variety of step
and efficiency unknown in any other Primate group. We can ask, and we
can but supply speculative answers as to the details of _how_ he did
it, but somewhere and at some time he learned first to become as good a
walking animal as later he became a talking one, and some at any rate
of the steps of the process are plain for all to read to-day.
How the Arch was Built.
Did I not know something of the severity of the judges in such a
Court of Appeal as we are facing in this case and of the opposing
counsel--of the jury I have less fear--I should be disposed to settle
on a half-sheet of note-paper the problem that non-arboreal man settled
ages ago for himself on the ground, by a familiar saying. It really
meets the non-scientific mind which is not weighed down by what Captain
Marryat used to call “top-hamper,” to answer _Solvitur Ambulando_. But
I hear judges and counsel both saying “This will never do,” and must
address myself to opening up the case.
If an adventurous gorilla and his mate, whom we may call gorilla
Columbi, had long ago made a bid for a life completely terrestrial
rather than partly arboreal, it is difficult to imagine how the feet
of this pair could have failed to adjust themselves and their separate
tarsal elements to a better if rudimentary form like that of man, and
that their progeny would not have followed or improved upon this.
Professor Keith,[70] in his work referred to, and Professor Wood Jones
in _Arboreal Man_, have much to say on the evolution of man’s foot
and arch, and I mention this _ab initio_ so as to be free from any
supposed claim to originality which is apt in the present extended
range of scientific progress to be as damaging to a man as for him
to proclaim his honesty or a woman her virtue. And I also formally
grant to the Mendelians and Mutationists, without offence and with
some possible relief to their minds, a period of leave from this poor
trench-warfare--_Plasto-ditēthēsis_ will not be obliged to call in at
the place of its hyphen any reinforcements from these of the higher
command.
[70] _Human Embryology and Morphology._
The assumed precursor of our human walker was probably more highly
evolved in his own special line than the real ancestor, but we have so
little yet of discoveries of whole skeletons of earliest man that the
bodily structure of gorilla C. may fairly be taken as a starting point,
indeed he is for this purpose a valuable lay-figure, almost artistic
for once, on which may be draped the following story of the making of
an arch. The ultimate verdict, which word I use in the old English
sense of a “true saying” rather than the most recent declaration of
those who “ride on white asses and sit in judgment,” does not therefore
invalidate the verisimilitude of this picture. One may go farther and
affirm that, given certain anatomical and physiological facts in an
earlier Primate stock, which marvellously resemble those of modern
man, and it must follow as the night the day that his more primitive
physical basis employed in a new mode of progression, that is of
terrestrial walking on two feet, will be converted by use and habit
into the construction of such new formations as will best agree with
the new style--in other words, in this instance, a plantar arch.
An Unique Phenomenon.
That a plantar arch is peculiar to man is a matter of fact, and
Lydekker in the _Royal Natural History_, Vol. I., p. 41, says of
the gorilla’s foot incidentally “there is no sort of resemblance
to the human instep in the whole foot,” and Professor Keith in the
work referred to “the arch is a human character.” One may see this
for oneself in living apes and monkeys and in the wonderful series
of drawings of apes in all kinds of postures in the _Royal Natural
History_, and indeed in the feet of dead apes and monkeys. All Primates
other than man walk on a flat sole.
Equipment.
Our adventurer starts with the following equipment of tools for making
his arch as he learns to walk entirely on the ground which it must
be remembered he can only do by unlearning _pari passu_ his highly
cultivated power of grasping with his foot. The old and the new cannot
flourish together. The evolving foot of man is an example of a slow
change in the function of an organ and consequent modification of
certain structures in it. He walks with his feet turning in, or in the
axis of the leg; his great toe is not in this axis but may even lie at
a right angle to the foot; he rests weight on his heel and even more on
the outer border of his sole, and thus the sole of one foot turns more
or less towards the other; and he puts a good deal of weight on his
toes which are frequently doubled over; and his gait, though erect, is
never completely so, and is clumsy in appearance.
_Bones_: his heel-bone is relatively long and pointed and slightly
arched below; the bones of his great toe are short and thick, and the
other four toes relatively long and slender. You can see at once it
is not primarily a walking foot. Any active boy of twelve could give
him points and a beating in a race for life in the open. Further, his
foot shows a much larger proportion of the whole foot in front of the
end of the great toe than is ever seen in man. The _ligaments_ which
bind the joints of his foot together, while the muscles play upon them,
are little different from those he will require for the girders of his
arch, except for such a throwing out of slips, and shifting under the
stresses and strains of such walking as his new gait involves.
The _muscles_ of his leg and foot are the most important by far of his
original equipment with which to set about making his arch: he could no
more do this out of his present muscles than a Hebrew could make bricks
without clay. It is these variable and plastic structures which are
most readily adapted by use in a fresh direction or increased degree.
He has the great flexors of the ankle and foot in his poorly-shaped
calf (this feature might be adduced as a human character and studied
in this manner if it were not of so elusive a nature) and the long
flexors of his four outer toes, the special long flexor of the great
toe, which in his case does not of course act in the axis of the other
metatarsal bones. He is lacking here in the special detached portion
of the _flexor accessorius_, which eventually becomes of use in
maintaining the arch, between the heel-bone and the tendons of certain
digits. He has, in a measure, the _oblique adductor_ muscle of the
great toe and the _transverse adductor_ muscle, more for future use
perhaps than of much present value. Like all apes and monkeys he has
a _peroneus longus_ with its tendon passing across the sole from the
outer border to the base of the great toe and a _peroneus brevis_, both
of them for everting the foot and supinating it. But here again he is
lacking, for he has no little _peroneus tertius_, which Professor Keith
speaks of as a muscle “peculiar to man” and “a special evertor of the
foot”--a muscle passing from the tendons of the _extensors_ of the toes
and inserted into the little toe. He has also the _tibialis anticus_
and _tibialis posticus_, the latter which flexes the ankle on the leg,
and the former which also flexes it and everts the foot; he has also
the special _extensors_ of the toes.
This enumeration of the bony, ligamentous, and muscular possessions of
gorilla C. is enough to show that, though he has little of new tools to
make, he has to modify greatly those he has learnt to use so well, so
that one can almost hear him echo the words of David to Saul as to his
new armour.
The problem of an arch remains to be solved by eversion instead of
inversion of the foot, growth in all directions of the heel-bone, and
the enlargement and straightening of the great toe, and the “setting”
of the foot in a certain degree of pronation and over-extension.
Description of the Arch.
The plantar arch is double, but the longitudinal one must be chiefly
considered here. It lies under the concave roof of the tarsal bones,
seven in number, and the metatarsal bones, and rests in a well-formed
foot in front on the heads of the latter, and behind on the inferior
surface of the heel-bone. The _astragalus_ alone of these bones in
contact with those of the leg, acts like a washer to the ankle joint,
and has no muscles attached to it. Three more of the _tarsal_ bones
need reference: these are the three _wedge-shaped_ bones which have
their bases on the dorsal and their apices directed towards the plantar
surface. With such a set of bony tools as this, all the requisites for
an arch are at hand. Let the half-tree, half-ground walker become a
complete ground-walker, and in the first place the manifest increase of
the action of the flexors of the leg will pull to an unusual extent
on the _tendo achillis_ and heel-bone, leading, in accordance with a
well-known law, to steady enlargement of the parts near to which it is
attached. The greater amount of weight thrown henceforth on the heel
tends in just the same direction, indeed, to general enlargement of the
whole bone. The _astragalus_ being in No Man’s Land, so to speak, takes
less part in the change than any other tarsal bone. The _wedge-shaped_
bones are exactly so constructed as to retreat a little in a dorsal
direction as the modified walking increases under the action of certain
muscles which will later be mentioned. This, in conjunction with
the projection backwards of the heel and the general growth of the
bone, permits, as far as the bony parts go, a gradual hollowing out
of the originally flat plantar surface, and the increasing eversion
of the foot places more weight on the front pier of the arch, that
is, the heads of the _metatarsal_ bones. The squeezing-up process of
the smaller _tarsal_ bones contributes also to the formation of the
transverse arch.
The _ligaments_ need no new invention on his part but only a more human
degree of development, and in particular the _calcaneo-navicular_
ligament and _internal lateral_ of the ankle undergo in the human foot
great development, and the long plantar ligament, originally part of
the tendon of the _gastrocnemius_, comes in to the aid of the arch and
goes to bind it together, so that these humbler structures follow in
the wake of the changing and enlarging bones.
The plantar fascia, though a powerful protective armour for the deeper
parts of the sole, cannot be held to enter into the formation of the
arch. The _initiative_ in this process lies with the muscles, and, even
if neither gorilla C. himself, nor his descendants, had altered the
muscles of his foot and just given up climbing for walking, there were
muscles strong enough and appropriate for modifying very profoundly his
simian foot, though he might not have arrived at an arch. He or they
might have become long-distance walkers, but never sprinters.
If the sole of the dissected foot is observed it is seen that the
plantar arch lies approximately over a triangle of which the base is
formed by the _transverse adductor_ muscle of the great toe, across
the heads of the metatarsal bones, and the two sides by the _oblique
adductor_ of the great toe and the _short flexor_ of the little toe. It
extends, of course, somewhat further back under the heel-bone, but this
is its highest part.
In the changing foot the _tibialis posticus_, which was originally a
flexor of the metatarsal bones, obtains a secondary attachment to
the _scaphoid_ bone, and the _tibialis anticus_ becomes inserted anew
into the internal _wedge-shaped_ and metatarsal bones. “Both of these
muscles, thus modified, help to maintain the arch of the foot. So does
the tarsal part of the tendon of the _tibialis posticus_.” (Keith).
The three _peronei_ muscles, especially the new _peroneus tertius_,
attached to the little toe, are called in by increased walking to
redress the balance of forces in the foot and produce that eversion,
with some supination, which is essential to the arch. No arch was
possible till these muscles came into some preponderance of action
over the _flexors_, so beloved of gorilla C. The _short flexor of the
digits_ becomes modified so that its attachment to the tendons of the
_long flexors_ in the sole has its _origin_ completely transferred
to the heel-bone in man (Keith). “It can thus act more powerfully in
maintaining the arch,” and finally the _flexor accessorius_, a muscle
which cannot fail to surprise the dissector when he first penetrates
into the deep layer of muscles of the sole, and which is a detached
piece of the _long flexor of the great-toe_, becomes especially
well-developed and helps to maintain the arch.
The order of events then is: first, increased and altered muscular
function; second, growth of bones and adjustment; third, binding
together of these by new or modified ligaments. If it were possible
to separate in this way the age-long formation of such a living tool
as the human foot, this is the order in which alone, I submit, the
sequence of events can be placed. It is a convenient, because simple
and plain example of initiative in evolution, and I cannot say how much
I owe to Professor Keith’s teaching on the subject.[71]
[71] It is not sufficiently noticed by some writers how important
is Professor Keith’s teaching as to the maintenance of the arch by
muscular action rather than ligamentous union. And it is a very
practical matter from my own point of view in connection with the
prevention of flat-foot in the young. If indeed the poor deformed
feet of the sufferers can only be corrected by attention to the
lowly-organised ligaments, and the muscles will not avail, I can but
add “God help them!”