CRANIOLOGY
Having finished the study of general biological questions and of the
body considered in its _entirety_, we may now pass on to analyse its
separate parts, treating in connection with each of such parts the
social and pedagogic questions which may pertain to it.
The _parts_ of the body which we shall take under consideration are:
the _head_, the _thorax_, the _pelvis_ and the _limbs_.
_The Head._--When we pass from the body as a whole to a more
particularised study of the separate parts, it is proper to begin with
the head because it is the most important part of the whole body. The
older anthropology, and biological and criminal anthropology as well
were very largely built up from a study of the head; a study so vast
and important that it has come to constitute a separate branch of
science: _craniology_.
The fact is that the characteristics manifested by the cranium are
chiefly in the nature of _mutations_ rather than _variations_,
and consequently the anthropological data relating to the cranium
correspond more directly to the characteristics of the species, or
in the case of man, to the characteristics of race. Hence they are
of special interest to the general study of anthropology. But when
these imitative characteristics, which are naturally constant and
have a purely biological origin, undergo _alterations_, they are to
be explained, not as variations, but as _pathological deviations_;
and for this reason criminal anthropology has drawn a very large part
of its means of diagnosis of _anomalies_ and of _degeneration_ from
malformations of the cranium.
Furthermore, the cranium together with the vertebral column represents
not only the characteristics of species, but also those of the _genus_;
in fact, it corresponds to the cerebro-spinal axis, which is the _least
variable_ part of the body throughout the whole series of vertebrates;
just as, on the contrary, the _limbs_ represent the _most variable_
part. Indeed, if we study separately the cranio-vertebral system and
the limbs, through the whole series of vertebrates, we shall discover
_gradual_ alterations in the former, and sudden wide alterations in
the latter. The cerebro-spinal axis (and hence the cranio-vertebral
system) shows from species to species certain progressive differences
that suggest the idea of a gradual sequence of modifications (from
the amphioxus to man) to which we could apply the principle, _Natura
non facit saltus_: while the limbs on the contrary, even though
they preserve certain obvious analogies to the fundamental anatomic
formation of the skeleton, undergo profound modifications--being
reduced in certain reptiles to mere rudimentary organs, developing into
the wing of the bird, the flying membrane of the bat, and the hand of
man.
Since it is not only a characteristic of species and race, but of
_genus_ as well, the cranium constitutes one of the most _constant_
anatomical features. For the same reason it is less subject to
_variations due to environment_, and from this point of view offers
slight interest to pedagogic anthropology. But since the cranium
contains the organ on which the psychic manifestations depend, we have
a deep interest in knowing its human characteristics, its _phases of
development_, and its normal limits.
HEAD AND CRANIUM
The term _Head_ is applied to the living man; the _Cranium_, from which
this branch of science takes its name, is the _skeleton of the_ _head_.
The cranium is composed of two parts, which may be virtually separated,
in the lateral projection, by a straight line passing through the
external orbital apophysis and extending to the auricular foramen,
thus separating the facial from the cerebral portion of the cranium.
Hence the _cranium_ is the skeleton of the head in its entirety, and is
divisible into the _cerebral cranium_ and the _facial cranium_.
_The Cranium._--The cranium is a complex union of a number of flat,
curved bones united together by means of certain very complicated
arborescent sutures, and forming a hollow osseous cavity of rounded
form. I will briefly indicate the bones which form its external
contour. On the anterior part is the _frontal_ bone, terminated by the
suture which unites it to the two parietal bones: the _coronal suture_;
while the two parietal bones are joined together by the _median_ or
_sagittal suture_, which forms a sort of _T_ with the other suture.
On the posterior side is the _occipital bone_, which is also joined
to the two parietal bones, by means of the occipital or _lambdoidal_
suture. Below the two parietal bones, in a lateral direction, are the
_two temporal bones_; and between the temporal and parietal bones
are situated the _great wings of the sphenoid_. The main body of the
sphenoid is at the base of the cranium. Besides these there is another,
internal bone, the _ethmoid_.
_The Face._--The skeleton of the face is composed of fourteen bones;
some of these are external and lend themselves to measurement; others
which are internal and hidden contribute to the completion of the
delicate scaffolding of this most important portion of the skeleton.
The principal bones of the face are: the two _zygomatic_ _bones_
(articulating with the temporal, frontal and maxillary bones); the
two nasal bones (articulating with the frontal and with the ascending
branch of the maxillary, and uniting above to form the bridge of the
nose; this is a bone of great importance in anthropology, because it
determines the naso-frontal angle and the formation of the nose); the
two upper maxillary bones, or upper jaw (articulating together in front
to form the subnasal region; laterally with the zygomatic bones; above
with the nasal bones; internally with each other, to form the palate,
and posteriorly with the palatine bones); the _mandible_ or lower jaw
(a single bone, and the only movable bone in the cranium), articulating
with the temporal bones by means of a condyle, and the separate parts
of which are distinguished as the _body of the mandible_ and the
_ascendant branches_, which are united to the cranium.
[Illustration: FIG. 39.--Note the line of division between the cerebral
and facial cranium; in addition to this the sutures are shown which
divide the frontal, parietal, occipital and temporal bones. PD. Coronal
Suture; DL. Sagittal Suture; AL. Lambdoidal Suture.]
The bones of lesser importance, which are interior and hidden are:
the two _lacrymal_ bones (situated at the inner angle of the orbitary
cavity), the _vomer_ or osseous septum of the nose; the two bones
in the nose which lie on each side of the vomer and are known as the
_turbinated bones_ (_concha nasalis_); and the two palate bones (which
form the backward continuation of the palatine vault constituted by the
maxillary bones).
_Human Cranium and Animal Cranium._--The dividing line between the
cerebral and facial cranium is of great importance in anthropology,
because the relative proportions between these two parts of the cranium
form a human characteristic, contrasting widely with the animal
characteristics; and they offer a simple criterion for determining the
higher or lower type of the human cranium. (Compare in this connection
Fig. 40, skulls of the higher mammals and of man.)
[Illustration: FIG. 40.]
The illustration represents a number of different animal skulls; and at
the top are two human skulls, the one of an Australian and the other
of a European. It will be seen that the proportions between the facial
and cerebral portions are very different; in the animals, even in the
higher orders such as the _primates_ (orang-utan, gorilla, etc.), the
_facial_ and _masticatory_ parts predominate over the cerebral.
One might even say that the skeleton gives us at a glance the
characteristic psychological difference; the animal _eats_, man
_thinks_; that is, the animal is destined only to vegetate, to feed
itself; man is an entirely different species; he has a very different
task before him; he is the _creative being_, who, through thought and
labour, is destined to subjugate and transform the world.
There are still other characteristic differences between the animal and
the human skull. The cerebral cranium of the ape is not only smaller
but it is furnished with strong bony ridges, to serve as points of
attachment for powerful muscles intended to protect the cranial cavity.
The human skull is completely devoid of such ridges; it is perfectly
smooth, with delicate contours; it might be described as "frail and
naked"; for the word nakedness precisely expresses the _absence_ of
those defences with which the cranium of the anthropoid ape is so
abundantly provided. Accordingly, the human cranium is _undefended_ by
soft tissues; and even the bony walls themselves are far from thick. If
we take a transverse section of the bones of the cranium, we find that
they are formed of two very thin layers of bone united by a porous,
osseous substance; the external layer is in direct contact with the
muscles of the scalp, and the internal layer with the brain. These
two layers differ widely in their degree of elasticity: the external
layer is so elastic that if it receives a bruising blow (provided this
is not so heavy as to surpass its limits of elasticity) it will yield
even to the point of touching the inner layer and then spring back to
its original position without leaving any perceptible trace of the
blow received (this is especially true in the case of infants),[36]
while the inner layer is so unelastic as to appear almost as brittle
as _glass_: so much so, for example, that the indirect shock of the
same contusion may cause it to splinter into fragments, which may
either penetrate the substance of the brain, or produce hemorrhages, or
inflammatory reactions in the meninges--and sometimes may constitute
the sole cause of epilepsy, and various forms of inflammation of the
brain (even resulting in idiocy), and sometimes of meningitis and death.
Contusions on the heads of children, and in general blows resulting
from falls or other causes, must be taken into serious consideration,
in the history of the individual, even though they have left no
profound traces _externally_.
This human characteristic of nakedness, of the _absence_ of powerful
bodily defences, is not limited to the head alone, but is diffused
over the entire morphological organism. Man, considered as an animal,
is weak; he is born naked and he remains naked, and destitute of those
natural defences which explain the endurance and the survival of other
species; neither the fur nor the plumage of mammals and of birds nor
the bony shields of reptiles and scales of fishes serve as defences for
this vertebrate, who has raised himself to the highest eminence in the
zoological scale; neither the muscular strength and powerful teeth of
the felines, nor the talons of the birds of prey have been his arms of
conquest.
Nevertheless, man who has conquered the earth and overcome all his
powerful biological enemies, owes his survival, equally with all other
living creatures, to his victory over other animals and over his
environment. Wherein lies the special strength of this little, feeble
being, who has become the lord of the earth? It lies in his brain.
The arms of this conqueror are wholly psychic. It is his intelligence
which has prevailed over the might of other animals and enabled him to
acquire the means of adapting himself to his environment, or else of
adapting his environment to himself. His intelligence, which sufficed
him as a weapon with which to achieve victory in the struggle for
existence, is also the means which still permits him to continue on the
road toward self-perfectionment.
The morphological importance attached by anthropologists to the
cerebral cranium depends precisely upon this: that it is the envelope
of the _brain_. If we examine the interior of the human cerebral
cranium, we find that it has adapted its bony contours so faithfully
to those of the soft tissues that it bears the imprint of the various
parts of the brain (cerebrum, cerebellum), the convolutions, and even
the blood-vessels of the meninges. Accordingly, a study of the cerebral
cranium amounts to an indirect study of the brain itself.
_Characteristics of the Human Cranium._--The characteristics of the
human cranium are all associated with the great development of the
volume of the brain. Let us assume that we have an elastic vessel,
representing in form an animal cranium, open at the base through an
orifice corresponding to the occipital foramen. If we inflate this
vessel, it will not only begin to enlarge at the expense Of its folds
(ridges), and to stretch and distend its walls (thinness and fragility
of the cranial bones); but furthermore it will undergo a change in
form, acquiring a more pronounced rotundity and _pushing upward_ in
its anterior part above the face. This part, rising erect above the
face, and determined by the volume of the brain, is the _forehead_.
Animals do not have an erect forehead; their orbits continue backward
in an almost horizontal line, giving them an extremely receding brow.
Corresponding to this preponderance of the cerebral portion, the facial
portion _retires_ below the brow, the mandibles do not extend beyond
the anterior axis of the brain, and are so far diminished in volume
that they assume, as compared with animals, a new function; in short,
the mouth is no longer merely the organ of mastication, but also the
organ of speech; its animal part has been spiritualised.
_The Evolution of the Forehead.--Inferior Skull Caps; the Skull_ _of
the Pithecanthropus; the Skull of the Neanderthal Man._ The forehead is
so distinctly a human characteristic that mankind has not needed the
help of anthropology in order to realise its importance--and as a sign
of superiority, nobility or sovereignty, has placed upon the forehead
the crown of laurel, or the crown of nobility or kingship.
Has the forehead always been a human characteristic, or have we
acquired it little by little? Such a problem is associated with the
evolution of the brain. There are in existence certain remains of
the skeletons of primitive men, which show them to have possessed a
cerebral cranium inferior in volume to that now attained by the human
species; and in these remains the forehead is also profoundly different
from that of to-day, in that it is much lower and slants backward,
while the supraorbital arches are very prominent. Such is the evidence
of the "cranial caps," discovered in the early geological strata.
In the tertiary strata of the island of Java, which in that remote
epoch of the earth's history must, together with Sumatra, have formed
part of the continent of Asia, which is considered as the "laboratory
of races," a skull was found by Dubois which raised the problem
whether it should be classed as that of an ape superior to those now
existing, or of a primitive man. Prior to this discovery, it had been
maintained that man did not make his appearance until the quaternary
period. This supposed primitive man was called by his discoverer the
Pithecanthropus, _pithecanthropus_ _erectus_.
Remains that are unquestionably human occur in the quaternary period,
in which however skeletons are very rare, as compared with relics
of human labour or social life, relics which are found scattered
everywhere throughout Asia and Europe as well (chipped flints). The
various remains of skeletons show us skulls much inferior to those of
modern man, but superior to that of the pithecanthropus. In treatises
of general anthropology reproductions are given of human crania known
as the Spy or Neanderthal type, belonging to the epoch when the
gigantic mammoth still roamed the earth. The forehead is very low and
receding and the orbital arches are enormously developed; while the
cerebral capacity calculated from the cranial dimensions is inferior to
that of modern man.
Consequently, as the brain increases in volume in the course of the
revolution of the race, the cranium not only shows a corresponding
volumetric increase, but at the same time _alters its form_, thus
producing the _forehead_ which little by little rises from a receding
to an erect position, and becomes high where it was formerly low, while
at the same time the prominent orbital arches disappear. Accordingly,
we may consider the forehead as the _skeletal_ _index_ of the cerebral
volume, and hence of the relative anthropological and intellectual
superiority.
In addition to its above-mentioned value, it also furnishes us with a
biological principle of much importance: the relation _between_ _the
volume and form_ of the cranium.
While the volume has a significance that is _relative_ to the mass of
the body, the significance of the form is _absolute_.
Let us examine these two skulls: normal human skulls of our own
epoch; one of the Celtic race (Fig. 46) and the other Sardinian (Fig.
43); that of the Celtic race is much larger and rounder; that of the
Sardinian is very much smaller and more elongated.
If we were considering only the _volume_, we might say that it was
simply a case of a _microcephalic_ and a _macrocephalic_: two terms
(microcephaly and macrocephaly) that fall within the province of
pathology. On the contrary, these two skulls are normal, but they
belonged to individuals characterized by differences of race; the one
(small skull) having a low stature; the other (large skull) having a
tall stature.
The volume of the head therefore bears a relation to that of the
body; the volume has a _relative_ significance. But the form in both
of them reveals a state of normality; the two skulls have a high and
erect forehead, and exhibit in their whole contour a fine and regular
development. Therefore the _form_ has an _absolute_ significance. It
even proves to us the _normality_ of the volume, a fact which could not
be determined by the volume alone.
Another mechanical correspondence between volume and form is disclosed
when we compare the skull of a new-born child with that of an adult.
The skull of the new-born child is much smaller in volume; but the
form shows the relatively enormous volumetric development of the brain;
in fact the skull is protuberant and the forehead bulges forward above
the face (_front bombe_), while corresponding to this index of cerebral
development is the enormous preponderance of the cerebral cranium over
the facial cranium, which is so small as to be almost reduced to a
simple rudiment.
Hence the form by itself alone reveals the infantile character of
the cerebral volume, which, in relation to the bulk of the body is
of far greater dimensions than in the adult. In fact, if a child
simply increased in volume and its growth was not the sum total of a
morphological evolution, the adult man would become a monster; his
macrocephaly would be so exaggerated that his neck could not sustain
the weight of the head (If the relations between the proportions in
infancy were maintained through life the adult man would have a head
with a perimeter of 130 centimetres, = 4 ft. 3 in.).
Aside from its mechanical relations to the volume, the _form_ has
characteristics dependent upon biological factors, such as the _sex_
and the _race_. The female cranium in fact has a straighter forehead
than the male and the orbital arches are absolutely wanting, while the
entire surface of the cranium is smoother and more rounded.
Similarly, the different races exhibit _forms_ determined by biological
factors and not by mechanical causes--for instance, the degree of
dolichocephaly (elongated cranium) and of brachycephaly (short cranium).
Hence the form is life's manifestation not only of the characteristics
proper to the species, but also of the mechanical adaptations demanded
by the material composing the body.
It may be said that the _volume_ and the _form_ of the cranium are
dependent upon two different biological potentialities: the volume is
mainly determined by the cerebral mass; the form, on the contrary, is
mainly determined by the bony structure--no matter how completely form
and volume coincide in their reciprocal mechanical relations.
That is, the attainment of a given volume of head depends upon the
development of the brain; the bone follows this development passively,
is the index of it, the skeletal representation of it, but never the
determining factor.
At one time it was thought, on the contrary, that a precocious
ossification of the cranial cavity would arrest the development of
the brain; _microcephaly_ was believed to be caused by a precocious
closing of the sutures of the cranial bones; and there was a certain
period when the surgical treatment of microcephaly consisted in the
removal of a portion of the cranial bone, in order to allow the brain
to develop freely.
[Illustration: FIG. 41. FIG. 42. Dividing line in human skull, as
compared with that of gorilla.]
[Illustration: FIG. 43.--Rounded ellipsoidal cranium.]
[Illustration: FIG. 44.--Brachycephalic cranium (vertical norm)]
[Illustration: FIG. 45.--Remains of spy cranium.]
[Illustration: FIG. 46.--Brachycephalic cranium.]
[Illustration: FIG. 47.--Egyptian cranium, 21st dynasty, ovoid type.]
[Illustration: FIG. 48.--Dolichocephalic cranium, from lateral norm.]
But the failure of such attempts afforded additional proof of the fact
that the volumetric development of the cranium depends upon the brain
alone.
If a precocious or abnormal suture occurs in the cranial bones, there
does not follow an arrest of development, but simply a _malformation_;
which is precisely in proportion to the potentiality of the brain,
which grows less where the suture has been formed, and in compensation
grows more than normally where the conditions of the bones permit
of cerebral expansion; and a deformity results. Microcephaly on the
contrary shows inferiority of form (smallness, receding forehead,
etc.), but not _malformation_.
_Anomaly of form_, therefore, results only from anomaly of skeletal
development, and is frequently found in conjunction with a _normal
development of the brain_.
Consequently _malformations_ of the cranium do not have the grave
significance of biological inferiority or of degeneration that they
were at one time believed to have; but frequently they must be
considered in connection with pathological conditions resulting for the
most part in delayed development in the embryo or in early infancy,
producing a thickening of the bone, or a partial suturation of the
points, or parts, or of the entire suture (punctiform synostosis,
partial or total); sometimes the sutures remain unaltered, and the
deformation must be attributed to various disturbances connected with
the nutrition of the skeleton in the course of intrauterine evolution
(hereditary syphilis, denutrition of the mother during pregnancy,
etc.). In short, a cranium that is abnormal in form is an indication of
pathological occurrences or of physiological errors that have resulted
in altering the normal growth of the individual.
There are many anomalies in the form of the cranium, but here we will
cite only the two principal ones, because they are the most frequent
and most likely to be encountered in individuals whose growth has been
retarded (from lack of nutrition) and consequently constitute signs of
physiological inferiority often associated with social caste. These two
forms are: scaphocephaly and plagiocephaly.
The scaphocephalic cranium (Figs. 51, 52), is characterised by being
very narrow and flattened laterally; while the forehead and the occiput
project in front and behind, the two parietal bones meet above almost
in an angle, so that, if it were turned upside down, the vault of the
cranium would have the appearance of the hull of a ship.
The _plagiocephalic_ cranium is a cranium which is unsymmetrical in
respect to its longitudinal axis; that is, it is not equally developed
on the right and on the left.
As a matter of fact, our bilateral symmetry is an ideal standard
rather than an absolutely attainable reality; we are all of us a
little larger on one side and a little smaller on the other, but to
so slight a degree as to escape superficial observation, so that
in general we have _apparently_ a bilateral symmetry--that is, we
appear to be symmetrical according to the testimony of our senses;
but a more delicate examination proves that this is not true.
Plagiocephaly therefore represents an exaggerated case of a normal
fact. Plagiocephaly may be simple or compound; it is simple when the
asymmetry is partial; namely, when it is confined to the anterior or
posterior portion; it is compound when it is total; and in such case
we find a complete diagonal correspondence: for instance, if the right
nodule in the frontal region is more prominent, the left nodule is more
prominent in the left occipital region, or _vice versa_. In general
it may be said that the various forms of _plagiocephaly_ are produced
by asymmetry of the _nodules_ or of the _flattened_ surfaces of the
cranium. Even in the case of _microcephaly_ and of _macrocephaly_,
which are substantially anomalies of _volume_, we find corresponding
characteristic abnormalities of form. The microcephalic cranium is of
inferior type, suggesting that of the ape--in other words, it is a
cranium which has mechanically adapted itself to a brain of inferior
volume: the macrocephalic cranium, especially if the abnormality is
due to _rickets_ or to _hydrocephaly_, calls to mind the infantile
type of cranium; it has the characteristic bulging forehead, while
mechanical adaptation frequently renders it very round (pathological
brachycephaly). We will take up this question again when we come to
speak in particular of _malformations_ and to describe the technical
methods of cranioscopy. What more particularly concerns us now is a
consideration of the _normal_ form of the cranium and its morphological
evolution.
[Illustration: FIG. 49.--Cranium of new-born child (lateral norm).]
[Illustration: FIG. 50.--Cranium of new-born child (vertical norm).]
[Illustration: FIG. 51. FIG. 52. Scaphocephalic cranium.]
[Illustration: FIG. 53.--Cranium of new-born child seen from above,
showing polyhedric contour due to nodules of ossification; fontanelle
of the bregma; and suture dividing the two frontal bones.]
[Illustration: FIG. 54.--Ellipsoides (classified by Sergi).]
=The Morphological Evolution of the Cranium through the= =Different
Periods of Life.= _Embryogeny. Order of Appearance of_ _the Points of
Ossification and of Synostosis of the Sutures._--In its successive
transitions through the different periods of life, the cranium not
only acquires successively greater volume, but it assumes forms
corresponding to the different grades of morphological evolution. We
may group its transformation under five different periods: 1. from
conception until birth (embryonic evolution); 2. from birth until the
end of the third year (infantile evolution); 3. from three years old
until twenty (youthful evolution); 4. from twenty to forty (adult age);
5. from forty to the end of life (involution).
_First Period._--In the earliest stages of intrauterine life the
cranium consists of a membranous skin, enclosing the primitive cells
of nerve tissue constituting the brain; it has a cartilaginous basal
part, destined later to form the _base_ of the skull (basioccipital and
basisphenoid bones). But all the rest (the vault or cap of the cranium)
remains in a membranous state, so that at this period the head of the
embryo has not yet acquired a definite form.
[Illustration: FIG. 55.--Cranium of new-born child. Showing nodules and
fontanelles.]
In the second month of intrauterine life the phenomena of ossification
have already begun to take place; that is, a fine network has formed,
spreading over almost the entire surface, which proceeds to fill up
its interstices with calcareous salts. This process, however, is more
rapid and more intense at certain points (points of ossification), from
which it cannot properly be said that the ossification _radiates_, but
rather that at these points the general process is intensified and
concentrated. There are five principal points of ossification: two
frontal, two parietal and one occipital, which appear clearly defined
and projecting like nodules, imparting to the cranium, when seen from
above, a pentagonal form, which is the normal form of the infant
cranium.
_Second Period._--At birth the cranium has not yet completed the
process of ossification, nor are the normal number of bones that will
eventually compose the adult cranium, as yet definitely determined.
Therefore the cranium of the new-born child has three distinct
characteristics:
1. It is not yet uniformly rounded, but polyhedral because of the
noticeable prominence of the five primitive nodules or centres of
ossification (2 frontal, 2 parietal, 1 occipital, Figs. 53, 55).
2. Since the process of ossification of the bones is not yet completed,
certain membranous portions or _cranial fontanelles_ still remain,
which are especially wide at the points where several bones meet. The
principal fontanelle is that of the bregma (at the juncture of the two
frontal with the two parietal bones, quadrangular). Next comes that of
the lambda, which is much smaller (juncture of the two parietal bones
with the occipital, triangular), and lastly the fontanelles of the
asterion and the pterion, on opposite sides of the temporal bones, the
former being situated behind and the latter in front.
3. Since the process of ossification is incomplete, the fusion of
bony portions into entire bones, such as they are destined to be
when complete development is reached, has not yet been accomplished;
that is to say, certain bones of the cranium are still divided into
several portions. For example, the frontal bone in the new-born
child is composed of two bones, separated by a longitudinal suture
that is destined to disappear, and the occipital bone is composed
of four parts, namely, the base, the squama and the two condyles
(basioccipital, exoccipital and superoccipital bones).
During the first period of three years, while the brain is increasing
notably and rapidly in volume, the cranium undergoes various and
interesting transformations. The pentagonal form of the cranium
tends steadily to become rounder, because the primitive nodules
are diminishing, or even disappear, although in this regard many
individual varieties result; and the processes of ossification reach
their completion. This is the most important period of growth, during
which the individual development of the perfect cranial form may be
attained, provided the rhythm of growth between the brain and its
envelope remains harmonious; or again, certain deformations may be
definitely established, owing to the intervention of some pathological
condition or a disturbance of nutrition, altering either the internal
volume or the normal process of ossification of the bony covering.
The first closing of the fontanelles takes place, in our race, in
those of the asterion (posterior to the temporal bones), and next
in those of the pterion; and it sometimes happens, as an anomaly of
growth that leaves no external trace in the living man, that a little
bone is formed, duplicating the shape of the fontanelle itself; such
little bones, very common in abnormal crania, are called _Wormian_
_bones_. They may occur in connection with any of the fontanelles, but
especially with that of the bregma.
[Illustration: FIG. 56.--Cranium of adult with abnormal medio-frontal
suture.]
The fontanelle of the lambda generally closes during the first year;
and the last of all the fontanelles to close is the largest, which is
situated toward the front of the head, at the _bregma_, and is well
known, even by the common people, and can easily be felt upon a child's
head; it generally closes toward the end of the second year; and its
characteristics may furnish valuable indications of abnormality or
insufficiency of the child's development. For example, if it diminishes
and disappears ahead of time, this may constitute the first symptom of
_microcephaly_, or at all events, of submicrocephaly (_i.e._, a case of
microcephaly that is not very pronounced). On the contrary, when this
fontanelle remains dilated and delays its normal closing, this is a
sign of organic weakness and debilitating disease (cachexia, rickets,
myxedema). Furthermore, the fontanelle in question may alter its
characteristic appearance in certain forms of sickness. In the case of
hydrocephaly it becomes distended, while in enteritis, on the contrary,
in which the organism parts with a large proportion of liquid, it
becomes depressed.
The _sutures_ also undergo notable changes during this period of life.
The first to become effaced is the metopic or medio-frontal suture,
which is destined to close and form a single bone; by the end of the
first year it is obliterated throughout the middle third of its length,
and thereafter the process of suturation spreads upward and downward
until it is completed at the end of the second year (Welcker, Haeckel,
Humphry). Sometimes, however, this suture is not obliterated until very
late, and there are anomalous cases where it has remained throughout
life, giving the forehead a characteristic form (pronounced frontal
nodules and a slight palpable furrow along the medial line of the
forehead).
During this same time a fusion has also taken place between the
occipital squama and the two lateral or condyloid portions; but the
resultant whole still remains separated from the _corpus_ or _base_ of
the occipital bone, which will not become welded into one solid piece
with the rest before the age of seven years.
At the age of three, the ossification of the cranial vault has been
completed. In place of being depressed and protuberant, as it was
at birth, the cranium has grown upward and forward in the frontal
region, assuming an almost definitive form; the volume of the cranium
has at the same time undergone an exceedingly rapid growth, attaining
proportions very near to those of an adult.
From the age of three onward the head grows slowly, and its
transformations are much slighter and fewer. The cranial capacity
which at birth is 415 cubic centimetres, becomes at the age of three,
1,200, at the age of fifteen, 1,393, and in the adult, 1,400 cu. cm.
respectively. Accordingly we might say that at the age of three a
sort of repose has been established in the growth both of the the
brain and of the cranium; this is the age at which an awakening begins
in the child of that intelligence which is to put him in touch with
the external world, and it is also the age at which he may begin his
education in school.
_Third Period._--There follows a slow and parallel growth of both
brain and cranium. The ossification of the cranium itself reaches
completion. At the age of seven the occipital is definitely solidified
into a single bone and between the years of fifteen and twenty the
body of the sphenoid also becomes welded to the occiput. This process
of synostosis begins from the interior of the cranium, and only
subsequently manifests itself externally. Consequently, the basilar
suture closes at the time when the last large molars, the so-called
"wisdom teeth," appear. After this period, the base of the cranium can
no longer undergo any sort of growth, and in the case of uneducated
persons the complete development of the cranium is definitely
accomplished.
_Fourth Period._--But in the case of cultured persons, those who form
the class of brain-workers, the brain continues to grow, although
extremely slowly, up to the age of thirty-five or even forty, thanks to
the sutures which still remain completely intact and which still make
an expansion of the bony envelope possible.
After this comes the beginning of the
_Fifth Period._--The period of involution, during which the synostosis
(closing) of all the cranial sutures will successively occur, until in
advanced old age the cranium becomes composed of a single bone, just as
in the embryo it was formed of a single membrane.
The synostoses which occurred in the early periods had an evolutive
significance and were associated with the growth of the body and
the intelligence. These later synostoses, on the contrary, have an
involutive significance and are associated with the physiological
decay of the organism and at the same time with that of the psychic
activities.
The first point at which synostosis takes place is in the region of
the obelion, that is, near the middle of the suture which, unites the
two parietal bones; shortly afterward, the fronto-parietal sutures
begin to unite along the pterion. At the age of forty-five, the obeliac
synostosis has progressed as far as the lambda, and that of the
fronto-parietal suture to the bregma; and at fifty the ossification is
very nearly accomplished, at least on the right-hand side (according to
Broca's series of crania). At seventy the squama of the temporal bone
unites with the parietal, and at eighty the entire cranium has become a
single bone.
These processes are subject to no small number of individual
variations; there have been cases of persons who, although very old,
still preserved many of their cranial sutures intact and their psychic
activities remained correspondingly alert (men of genius). Conversely,
the closing of the sutures sometimes begins as early as the
thirty-fifth year. A diagnosis of age, as determined by the skeleton,
is consequently only approximate.
During the periods of growth the cranium may exhibit transitory
anomalies; it is very common to encounter in the heads of children of
the lower social classes, who are consequently subject to denutrition,
_malformations_ which represent various degrees and forms of
_plagiocephaly_, and which subsequently disappear completely, as the
development of the cranium advances. Anomalies of form must therefore
be judged differently in the case of the child than in that of the
adult.
It may even happen that the five primitive nodules persist for a
long time and even remain as a definitive form of the adult cranium
constituting, according to Sergi, a distinct variety, the _pentagonal_
cranium. But this is quite rare. From the frequency with which this
form is to be observed in schools attended by children of the poorer
classes, it is better to regard it as due to a delay in morphological
evolution, which will probably disappear later on.
NORMAL FORMS OF THE CRANIUM
We are indebted to Sergi for an exact knowledge of the _normal_
_forms_ of the cranium. Such forms are racial characteristics and are
_invariable_, as Sergi has succeeded in proving by a comparison of
the most ancient forms of the cranium with recent forms. Accordingly
this authority takes the cranial formation as the basis for his
classification of races. We have no direct interest, so far as concerns
the special scope of our own science, in the value of this theory
of classification--a theory, by the way, already divined, although
very imperfectly and under a different form, by French and German
anthropologists. Sergi's studies of cranial forms interest us solely
as a diagnostic test of _normality_ as compared with _abnormality_.
For it is due to these researches that certain forms that used to be
considered pathological, have come to be recognised as normal.
The _normal forms_ of the cranium may be grouped, according to Sergi,
under nine primary varieties, each of which includes _sub-varieties_.
These nine varieties are named as follows:
I. Ellipsoid; II. Ovoid; III. Pentagonoid; IV. Rhomboid; V. Beloid;
VI. Cuboid; VII. Sphenoid; VIII. Spheroid; IX. Platycephalic.
[Illustration: FIG. 57.--_Ellipsoides depressus_ cranium.]
I. _Ellipsoid_ (Fig. 58).--This form is recognised by inspecting
the cranium according to the vertical norm (see in the chapter on
_Technique_ the method of cranioscopy).
The cranial contour recalls an ellipse in which no trace of the nodules
remains, and in which the occiput is not in the least flattened; while
the anterior half of the cranium closely corresponds to the posterior
half.
The sub-varieties are differentiated by their greater breadth and
length, by the form and protrusion of the occiput, and also by the
height of the cranium measured vertically.
[Illustration: FIG. 58.--Ellipsoid cranium.]
[Illustration: FIG. 59.--Ovoid cranium.]
Accordingly, the sub-varieties have a binominal nomenclature
indicating, in addition to the fundamental characteristic (variety)
the qualitative characteristic of the sub-variety (_e.g., ellipsoids_
_depressus_; compare Fig. 57, showing a cranium seen laterally).
II. _Ovoid._--This form of cranium, seen from above, is that of an
ovoid, with the broader portion corresponding to the parietal bones,
at the point where the characteristic embryonal nodules are situated.
The protrusions of the parietal bones are apparent (swellings) but not
angular (nodules). The occiput protrudes and is broad (Fig. 59).
[Illustration: FIG. 60.--Pentagonoid cranium.]
[Illustration: FIG. 61.--Rhomboid cranium.]
III. _Pentagonoid._--In this form, persistent traces of the five
primitive embryonal nodules are still plainly visible, giving the
contour of the cranium, when seen vertically, the appearance of a
pentagon. The protuberances, however, are quite smooth and not pointed,
as in the embryonal cranium.
[Illustration: FIG. 62.--Beloid cranium.]
IV. _Rhomboid._--This form is similar to the pentagonoid, excepting
that the parietal breadth is much more notable in proportion to the
forehead, which is much narrowed and has lost its nodules.
[Illustration: FIG. 63.--Ovoids (classified by Sergi).]
[Illustration: FIG. 64.--Pentagonoides acutus (Sergi's collection).]
[Illustration: FIG. 65.--Beloides lybicus (classified by Sergi).]
[Illustration: FIG. 66.--Platycephalus orbicularis (classified by
Sergi).]
[Illustration: FIG. 67.--Platycephalus ovoidalis (classified by Sergi).]
[Illustration: FIG. 68.--Spheroidal cranium, vertical norm (Sergi's
collection).]
V. _Beloid._--The beloid, or arrow-head cranium is like the ovoid with
the occiput more flattened, so that the widest portion is further back
than in the ovoid; toward the front it becomes narrower, constituting
altogether an admirably shaped type of head.
[Illustration: FIG. 69.--Cuboid cranium.]
VI. _Cuboid._--This form is most clearly perceived when the cranium
is seen either sidewise or from the rear. Not only the face, but the
lateral and occipital walls as well are flattened; so also is the
forehead, which in general is quite vertical.
VII. _Sphenoid_ (cuneiform).--The broadening between the two parietal
bones is usually far back and very evident, while the cranium narrows
toward the front. The occiput is flattened.
[Illustration: FIG. 70.--Sphenoid cranium.]
VIII. _Spheroid._--Seen vertically, it presents the appearance of
a very broad ellipse; all the curves tend to become spherical. The
forehead, however, is not notably vertical.
IX. _Platycephalic._--The fundamental characteristic of this type
of cranium is that it is flattened on top, or rather, since such
flattening cannot be absolute, the arch of its vault is a segment of
a circle of very large diameter (Sergi), with the result that this
cranium has the appearance of being very low vertically and very broad
laterally. When seen vertically it may present a wide variety of
contours, ellipsoid, ovoid, pentagonoid, etc., but its distinguishing
characteristic remains that of the flattened vault.
[Illustration: FIG. 71.--Spheroid cranium.]
=Sub-varieties.=--_Sphenoids_ _trapezoids_, or _trapezoid cranium_.
Observed from the vertical norm, this form appears as a variety of
the _sphenoid_; and when seen laterally it is characterised by the
lines of its contour forming a _trapezium_. Starting from the vertex
of the cranium one line slants toward the forehead and another toward
the occiput, which is very massive. In the figure given below, the
quadrangle drawn in solid lines serves to indicate the correct position
of the cranium, while the trapezium formed of dotted lines gives us its
characteristic form.
[Illustration: FIG. 72.--Trapezoid cranium.]
Among the forms described by Sergi, are several which were formerly
held to be abnormal, such, for instance, as the _platycephalic_
_cranium_ and the _pentagonoid_. Similarly, when the surfaces of the
cranium showed a tendency toward flatness, or when there were cranial
protuberances, even though these were destined to disappear, they were
regarded as malformations. Before this high authority offered us his
guidance, there were certain forms, frequently encountered, that it
was difficult to define, for example, the trapezoid cranium, which
often presents a notable vertico-occipital flattening, with the vertex
notably higher than the forehead.
There are also certain forms of cranium having the frontal region more
restricted than the parietal region, or slanting down from a much
elevated vertex, which have been proved to be _normal forms_; while
still another error previously made was that of trying to judge the
_forehead_ on the criterion of a single model, deviations from which
were much too readily relegated to the category of abnormalities. The
most regular and beautiful forms, and the ones that are commonest in
our racial stocks are the ellipsoid, ovoid and sphenoid. In my work on
the women of Latium, precisely one of the points that I noted was the
frequent occurrence of certain sub-varieties of the _ellipsoid_ and the
_sphenoid_.
In order to recognise the _forms of the cranium_, a certain training
is necessary which each one must acquire for himself. Observations of
the cranium will make it easier to judge of the form in relation to the
_head_, at least, when the latter is not too much hidden by the hair,
as often happens in the case of young children.
A knowledge of the _normal_ forms of the cranium will also guide us
in our judgment of many abnormal forms, which very often present the
appearance of _exaggerations_ of normal types.
Thus, for example, the _acrocephalic_ cranium (much raised in the
parieto-lambdoideal region and sloping forward toward the brow, while
the occipito-lambdoideal region is flattened) recalls the _trapezoid_;
and the clinocephalic cranium (in which the coronal suture forms a
slight girdle-like indenture and divides the contour of the cranium,
when observed along the vertical norm, in two curves, a lesser anterior
and a greater posterior curve, resembling a figure of 8) recalls
certain varieties of ovoid cranium described by Sergi. This brings us
to a principle that is very interesting to establish, namely, that
frequently _anomalies_ represent _exaggerations_ of the racial or
family type.
THE CEPHALIC INDEX
Retzius was the first to take the _cranium_ under consideration
as a basis for a classification of the human races; and he
attempted to determine a concept of its _form_ by means of a
numerical formula expressing the relation between the length and
width of the cranium (cephalic index). Thus he distinguished the
races into _brachycephalics_, or those having a short head; and
_dolichocephalics_, or those having a long head. Following Retzius,
who may be regarded as the founder of craniology, Broca adopted,
completed and expanded this method, deriving from the cranium, or
rather from the particular character given by the cephalic index, a
_key_, as it were, suited to unlocking the intricate mysteries of
hybridism among the human races. Consequently the cephalic index was
not confined, as regards its importance, within the same limits as all
the other indexes, but was raised by the French school, warmly seconded
by Italian anthropologists, to the dignity of a fundamental determinant
of the _ethnic type_, as definitely as, for example, the vertebral
column serves as basis for a classification including all species of
vertebrates.
The Germans refused to accept the cephalic index as determining
the classification of races; but while seeking to prove themselves
independent of it, they continued to regard the _form of the cranium_
as a basis of classification (Ruetimeyer, von Hoeller, and to-day
Virchow), but without ever having identified, as Sergi has now done,
existing _forms_ as normal types of race.
The _cephalic index_ is obtained by the well-known formula expressing
the relation between the _maximum transverse diameter_ of the skull
(see "Technique") and the _maximum longitudinal diameter_ reduced to
100, and is expressed as follows: Ci = 100xd/D (the cephalic index is
equal to a hundred times the lesser diameter divided by the greater; in
the present case the lesser diameter is the transverse).
This _proportion between linear measurements_ cannot properly sum
up the _form_ of the cranium. We can, for example, conceive of a
microcephalic cranium having a normal _cephalic index_, since the
relation between the two maximum diameters necessary for deducing the
index, does not tell us, for example, either the dimension of the
cranium or the form of the forehead.
If, for instance, we should imagine a photograph of a cranium enlarged
a hundred diameters, the reciprocal relations between the length and
the width would still remain unchanged.
In order to demonstrate that the cephalic index does not determine the
form of the cranium, Sergi makes use of a number of different geometric
figures, such as a triangle, an ellipse, a trapezoid inscribed within
equal rectangles, and which consequently have an equal base and equal
altitude, that is, the same proportion between length and width.
It follows that skulls corresponding more or less closely in shape,
trapezoidal, trigonocephalic, ellipsoidal, plagiocephalic, and hence
both normal and abnormal, can be expressed by a cephalic index having
the same identical figures.
But, although the cephalic index is far from being _descriptive_ in
regard to the form of the cranium, it constitutes an anthropological
datum that has two advantages: 1. It depends upon measurements and
is therefore accessible to those who, not being anthropologists,
lack the trained eye that can distinguish with careful accuracy the
true _forms_ of the cranium in their manifold variety. Furthermore,
since the measurement of maximum diameters is sure and easy and may
be obtained with exactness, regardless of the thickness of the hair,
it may be applied in anthropological research to all subjects. 2. The
cephalic index, even if it does not give us the form, does give us a
fact which has a bearing upon the form, namely, whether the cranium is
long or short; in other words, it substantially represents the most
real and evident difference between the different types of cranium.
And since the cranium has a visibly spheroid form, that is, with
smooth and rounding surfaces, and constantly adheres to this generic
delineation, the fact of being longer or shorter introduces a definite
differentiation into the general and accepted form, and gives a very
simple and concise indication of it, that conveys the idea more clearly
than a description would.
Granting the _practicality_ of this line of research, the cephalic
index may also be accepted as an index of form, so long as there is no
intention of going deeply into minute differentiations for systematic
purposes. Professor Sergi himself, author of the system that forms
the basis of the study of cranial forms, urged me to exclude from a
practical course in pedagogic anthropology the classification of forms,
limiting the concept of form to that included in the cephalic index.
The cephalic index has the additional advantage of having been
extensively studied and consequently of having an abundance of mean
averages for comparison that are of great practical use. Furthermore,
the idea it gives regarding the cranium by means of one simple figure
serves to convey certain fundamental principles with great clearness.
In dealing with figures that determine an anthropological datum of
such high importance, it is necessary to define its limits and its
nomenclature.
Various authors have introduced their own personal classification
of the cephalic index, and no small confusion in nomenclature has
resulted; so much so that a need was felt of establishing a uniformity
of numerical limits and of the relative terminology, in other words, of
simplifying the scientific language.
Accordingly, a congress was held at Frankfort in 1885, at which the
following nomenclature was established by international agreement:
CEPHALIC INDEX.--_Nomenclature established at Frankfort_
Dolichocephalia = 75 and below
Mesaticephalia = from 75.1 to 79.9
Brachycephalia = from 80 to 85
Hyperbrachycephalia = 85.1 and above.
Previous to this, the most widely varied classifications were in use,
and the leading authorities had all introduced into the literature of
the subject their own personal classifications. Here are some of the
more important:
BROCA:
Dolichocephalics = 75 and below
Subdolichocephalics = from 75 to 80
Subbrachycephalics = from 80 to 83.3
Brachycephalics = 83.3 and above.
RANKE:
Dolichocephalics = 74.9
Mesaticephalics = from 75 to 79.9
Brachycephalics = 80 and above.
KOLLMAN:
Dolichocephalics = 73.9 and below
Mesaticephalics = from 74 to 79.9
Brachycephalics = from 80 to 86.9
Hyperbrachycephalics = 87 and above.
RETZIUS and
DAVIS:
Dolichocephalia = 79 and below
Brachycephalia = 80 and above.
TOPINARD: { 64 and below = Ultradolichocephalics.
{ 65 \
{ 66 }
{ 67 } True dolichocephalics.
{ 68 }
Dolichocephalics { 69 /
{ 70 \
{ 71 }
{ 72 } Subdolichocephalics.
{ 73 }
{ 74 }
{ 75 \
{ 76 / True mestaicephalics
Mesaticephalics { 77 (_Mean average._)
{ 78 \
{ 79 / Submesaticephalics
{ 80 }
{ 81 }
{ 82 } Subbrachycephalics.
{ 83 }
{ 84 /
Brachycephalics { 85 \
{ 86 } True brachycephalics.
{ 87 }
{ 88 }
{ 89 /
{ 90 and above = Ultrabrachycephalics.
It remains to determine the extreme _limits of oscillation_ of the
index, both in relation to the normal mean and in relation to the
fluctuations of this important ethnic datum in a given population.
Topinard, as we have seen, gives as his mean figures for the extreme
normal limits among the human races 64 and 90.
Deniker gives, as his mean averages for the human races, the following
figures: For dolichocephaly, 69.4 (natives of the Caroline Islands;
Australia); For brachycephaly, 88.7 (the Ayssori of the Transcaucasus;
Asia).[37] But we know that a mean is obtained from figures either
greater or smaller than the mean itself, so that the limits of
_individual variation_ must exceed that of the given figures.
Accordingly the oscillation of the normal cephalic indices may be given
as ranging from 70 to 90.
In regard to abnormalities (extreme human limits of the cephalic index)
the authorities give 58 for dolichocephaly (scaphocephaly) and 100
for brachycephaly (in which case the cranium is round and known as
_trochocephalic_; it is met with among the insane).
Between oscillations of such extremely wide range in the normal
cephalic index, the number chosen as a medial figure to serve the
purpose of dividing the dolichocephalics from the brachycephalics is
that of 80, which is included within the division of brachycephaly.
In spite of the nomenclature established at Frankfort, there is a
distinct scholastic advantage, because of the greater simplicity of
memorising and fixing the idea, in reverting to the nomenclature of
Retzius, who classes as brachycephalics all crania from 80 upward, and
as dolichocephalics all those below 80. It is certainly strange to
class all crania from 80 to 90 without distinction as brachycephalics,
and then to alter the name and call a cranium with an index of 79.9
a dolichocephalic. It has been found that there is always a slight
difference between the index taken from measurements of the cranium
and that obtained from measurements of the _head_. According to Broca,
it is necessary to subtract _two units_ from the cephalic index taken
from a living person, in order to obtain that of the cranium; thus, for
example, if the cephalic index (taken from life) is 80, the cranial
index (taken from the skeleton) would be 78. Such differences are due
to the disposition of the soft tissues. Consequently, even according
to the simple subdivision of Retzius, a person who was brachycephalic
during life, would become dolichocephalic after he was dead.
But this is what always happens in biology, whenever we try to
establish _definite_ limits. Life undergoes an insensible transition
through successive limits and forms, and this fact constitutes the
grave difficulties and the apparent confusion of biological systems.
In determining degrees of difference, it is necessary to have recourse
constantly to _special methods_, which teach us to recognise general
properties and to use them as a basis in dividing living creatures into
separate groups (see in the section on _Method_, "Mean measurements and
formation of series in relation to individual variations").
Hence, for mnemonic purposes, we need remember only the single number,
80.
But if we wish to adopt the nomenclature of Frankfort, it is necessary
to keep in mind two figures denoting limits, 75 (inclusive) for
dolichocephaly, and 80 (inclusive) for brachycephaly.
75 mesaticephalics 80 85
dolichocephalics brachycephalics ultra
These constitute, as it were, two centres, beyond which, on this side
and on that, we may picture to ourselves the _individual variations_
drawn up in martial line. In this case, the space between 75 and 80,
in other words, the limits of mesaticephaly, may be interpreted as due
to oscillations between dolicho- and brachycephaly according to the
laws of variability, which is analogous to what takes place in the case
of oscillations in the opposite direction (70-75 dolichocephaly; 80-85
brachycephaly). From this point of view, these two numbers, 75 and 80,
constitute _median centres_ of two different types.
But according to Broca and his school--and this view is accepted by
many anthropologists--mesaticephaly should be regarded as constituting
a _fusion_ of the two other types, the brachy- and dolichocephalic,
whence it follows that mesaticephalics would be _hybrids_. Other
authorities, on the contrary, exaggerating the conception of the
fixity of the cephalic index in a given race, admit the existence of
mesaticephalic races.
[Illustration: FIG. 73. Map of the Cephalic Index in Italy.]
But it has been observed that the greater number of mesaticephalics
are to be found in regions where dolichocephaly prevails; in
certain districts of Africa, as for example, in Somaliland, not a
single brachycephalic exists, yet none the less the mesaticephalics
are numerous. Accordingly, mesaticephaly may be classed with
_dolichocephaly_ and regarded as one of its variations, while it seems
to be independent of brachycephaly. Therefore the nomenclature of
Retzius may for many good reasons be chosen and adopted in our schools.
In conclusion, we shall regard the brachycephalics and dolichocephalics
as the two fundamental types; and shall adopt the figure 80, included
among the brachycephalics, as the limit of separation. The different
grades of dolicho- or brachycephaly are to be determined by _mean
averages_, and the oscillations due to individual variations, by
_series_.
Hence it is important to determine the _mean average_ and the
oscillation of the cephalic index for the different races; and this is
of interest to us as educators, in order to establish the limits of
_normality_.
The practical method of studying the cephalic index is according to
geographical distribution.
Here are a few general data of the cephalic index relative to its
distribution:
The most dolichocephalic of all peoples are found in Melanesia,
Australia, India and Africa. In the Fiji Islands the mean cephalic
index is 67; in the Caroline Archipelago it is 69; in various regions
of India, 71; that of the Hottentots, 74; of the Bantus, 73. Belonging
to the dolichocephalics or mesaticephalics are the populations of
the extreme south of Europe (Mediterranean race) and at the extreme
north (English, Scotch). On the contrary, the races of western Europe
and of central Asia are brachycephalic (Celts, Mongols). The most
brachycephalic of all these peoples are met with in the Transcaucasus;
their mean average is 88.7. There also exists a notable brachycephalic
type in France (Savoyards, 86.9; inhabitants of the upper Loire,
87.4); also in Dalmatia, 80, while the Lapps of Scandinavia are also
ultrabrachycephalic, 87.4.
On very general lines, it may be said that the dolichocephalics are
the Eurafrican races (including the Mediterranean race, with which
the first civilisations are associated: Egyptian, Greek and Roman)
who migrated from the Mediterranean basin into Europe; and the
brachycephalics are the Eurasian races, who on the contrary migrated
from continental Asia across western Europe (the Aryans).
As far as regards Italy, its population is by no means evenly
constituted. The median index given by Livi for Italy, deduced from
observation of more than 29,000 subjects is 80; in regard to regional
distribution, the results are shown in the following table:
Piedmont 85.9
Emilia 85.2
Venctia 85.0
Lombardy 84.4
Umbria 84.1
Marches 84.0
Liguria 82.3
Tuscany 82.3
Campania 82.1
Abruzzo and Molise 81.9
Latium 81.0
Basilicata 80.8
Apulia 79.8
Sicily 79.6
Calabria 78.4
Sardinia 77.5
Let us remember that if the cephalic index were measured directly from
the cranium, the result would be one or two units less, hence the mean
average of the cranial index would be about 78.
The accompanying map represents still more clearly the geographical
distribution. The results show that in Piedmont, in Emilia, and in
Northern Italy in general the inhabitants are more brachycephalic;
while in the south and more especially in the island possessions we
find the more dolichocephalic part of the population. The highest
degree of dolichocephaly is found in Sardinia.
But if, instead of the cartographic summary herewith reproduced, we
could examine the exhaustive one with which Livi has illustrated his
great work on Anthropometry, we should discover that the distribution
does not follow the great _regional lines_; but that as a matter of
fact certain _human groups_ exist, isolated like little islands, which
have a cephalic index in marked contrast to that of the remaining
population of the same region.
Thus, for example, at Lucca, in the midst of a brachycephalic
population, there is a pronouncedly dolichocephalic group; and in the
midst of the dolichocephalic population of Abruzzo and the neighbouring
provinces, there exists at Chieti a strongly brachycephalic group.
Besides these and similar groups contrasting with the regional type,
there exist a multiplicity of differences, from one successive boundary
line to another, so that the _limits_ _of the cephalic index_ may be
determined with great minuteness in the various regions.
Livi's large charts lend themselves with great clearness to this sort
of analytical study, which would be found to be very profitable to
teachers.
It is also quite instructive to compare the different charts
representing various anthropological data of ethnical importance;
such, for example, as that of the distribution of stature and that
of the distribution of pigmentation. These data are regarded by
anthropologists as attributes of race. Well, in these three charts it
is evident at the first glance that there is a notable resemblance
in distribution, so much so than an eye untrained to observation
would be likely to confuse them. The cephalic index, the stature, the
colour of the skin are consequently of almost uniform distribution.
Corresponding to the most pronounced brachycephaly, we have the
tallest stature and the fairest complexion; corresponding to the most
pronounced dolichocephaly, we find instead the lowest stature and the
most brunette types. Such an accumulative coincidence, in certain
communities, of characteristics, in contrast to those that are found
combined in certain other communities, reveal the existence in Italy
of _two different races_. One of these races seems to have descended
from over the Alps; the other, to have landed on the shores of the
Mediterranean. The first belong to the Eurasians; the second to the
Eurafricans.
In my work upon the population of Latium, the mean cephalic index
obtained by me is 78. The distribution according to the localities
studied affords the mean averages noted in the following table,
in which I have also recorded the maximums and minimums, and the
percentage of brachycephalic and dolichocephalic individuals who
contributed to the given means:
CEPHALIC INDEX AMONG THE PEOPLE OF LATIUM
(ACCORDING TO MONTESSORI)
--------------------------------------------------------------------
|Mean | | | Dolicho- |Brachy-
Provinces |cephalic |Minimum |Maximum |cephalics, |cephalics,
|index | | |per cent. |per cent.
----------------+---------+--------+--------+-----------+-----------
Rome | 78 | 73 | 89 | 63 | 37
_Castelli Romani_ | 76 | 70 | 79 | 100 | --
Tivoli | 80 | 76 | 87 | 59 | 41
Velletri | 79.5 | 75 | 86 | 50 | 50
Frosinone | 80.7 | 75 | 87 | 43 | 57
Civitavecchia | 78.5 | 78 | 80 | 65 | 35
Bracciano | 77 | 75 | 80 | 65 | 35
_Orte_ | 83.6 | 75 | 90 | 11 | 89
Acquapendente | 79.4 | 76 | 81 | 60 | 40
--------------------------------------------------------------------
The results show a preponderance of brachycephalics or of
dolichocephalics in the places where the mean cephalic index is
respectively highest for brachycephaly (Orte) or for dolichocephaly
(Castelli Romani). Furthermore, the extreme maximum and minimum
figures are found to be included in these groups (90 at Orte and 70 at
Castelli).
It should be noted that at Castelli Romani the mean average is
mesaticephalic (76), notwithstanding the absence of brachycephalics;
this average is based on figures showing an extremely pronounced
dolichocephaly (ranging to 70!). The groups at Castelli and at Orte
also showed characteristics in respect to stature (see page 111); at
Orte the mean stature is 1.61 m., with a maximum of 1.70 m. (very tall
statures for women), and at Castelli the mean stature is 1.47 m., with
a minimum of 1.42 m. (low statures).
Similarly, in regard to pigmentation, I found at Orte a prevalence of
blonds, and at Castelli of brunettes. Hence the conclusion may be drawn
that at Castelli and at Orte there exist groups of human beings who are
of almost pure race, in the midst of a population in which racial types
have become attenuated or hidden; but in centres like these we still
find persistent testimony as to the ethnic factors that combined to
form the people of Latium: the one, a blond, tall, brachycephalic race;
the other, dark, small, and dolichocephalic.
_The Cephalic Index at Different Ages of Life._--Another quality that
renders the cephalic index of great importance is that it remains
constant in the course of growth, since the two maximum diameters, the
antero-posterior and the transverse, increase at very nearly the same
rate, excepting during the earliest years, at which time the length of
the cranium increases slightly more than the width. According to some
authorities it is in the second year, according to others it is in the
fourth or seventh, that the cephalic index becomes constant (Binet,
Deniker, Pearson, Fawcette, Ammon, Johannson, and Westermarck).
The following table is one that I have drawn up on the basis of
Quetelet's figures:
CEPHALIC INDEX
---------------------------------------------------
Age | Males |Females| Age | Males |Females
---------+-------+-------+---------+-------+-------
At birth | 83 | 83 | 11 years| 80 | 79
1 year | 80 | 80 | 12 years| 80 | 79
2 years | 80 | 80 | 13 years| 80 | 79
3 years | 80 | 80 | 14 years| 80 | 79
4 years | 79 | 79 | 15 years| 80 | 79
5 years | 79 | 79 | 16 years| 80 | 79
6 years | 79 | 79 | 17 years| 80 | 79
7 years | 79 | 79 | 18 years| 80 | 79
8 years | 79 | 79 | 19 years| 80 | 79
9 years | 80 | 79 | 20 years| 80 | 79
10 years | 80 | 79 | --- | -- | --
---------------------------------------------------
Since it has been observed that the cranium in the course of its growth
may assume forms, amounting even to apparent malformations (due chiefly
to "bumps," either symmetrical or asymmetrical), which disappear during
the evolution of the individual, the _cephalic index_, for _the very
reason_ that it does not represent a faithful description of the form,
gives us precious aid in judging the cranium of the child, because it
_accurately determines the proportions_ _between length and breadth_
which are destined to persist even in the adult, and hence serve to
give, even in infancy, a sure indication of the ethnic type to which
the child belongs.
[Illustration: Per cent.
Negro Children
Children born in Syria
Children born in Russia
Children born in Germany
FIG. 74.]
We owe to Dr. Ales Hrdlicka the extremely important graphic chart,
which I will proceed to summarise, of the cephalic indices of children
of various races: the central dotted line corresponds to the index 80:
consequently the brachycephalics are indicated on the right, and the
dolichocephalics on the left (Fig. 74).
In the case of Italy, the graphic line extends between the two extreme
figures of 70 and 90, which are precisely the extreme limits that we
have already noted for individual adults, in the case of the women
of Latium: moreover, the curve is perceptibly symmetrical, although
the brachycephalics are in the majority; a fact already established
by Livi's mean averages. One might say that this curve was a graphic
representation of Livi's two-colour method in his map of the cephalic
index: one-half of Italy is brachycephalic and the other half is
dolichocephalic; but since brachycephaly prevails in the northern
half, a wider extent of territory is occupied by brachycephalics.
In America, where emigration brings every variety of humanity,
the curve is even more symmetrical, and rests on a broader basis,
representing widely separated extremes. Ireland also shows a very
perceptible symmetry, the population being a mixture of Celts
(brachycephalics) and of Scotch (northern blond dolichocephalics).
In Germany there is a prevalence of brachycephalics; we are here
approaching the eastern regions from which the Eurasian race came
through emigration. Here the Slavs and Celts (brachycephalics who
immigrated into Europe at various epochs) are intermingled with a
notable percentage of dolichocephalics (Teutons).
[Illustration: Per cent.
Children born in Ireland
White Children born in America
Children born in Italy
FIG. 74.]
But in Russia, a region still further east, and similarly in Syria, we
find an almost pure race: the curves lie wholly within the field of
brachycephaly.
On the contrary, the dark-skinned children given in the last chart, and
belonging to African races and tribes of American Indians, are all of
them _dolichocephalic_.
According to Binet and other writers, the _cephalic index_ and the
_cranial volume_ are the two anthropological data on which the
criterion of _normality_ of children's heads must be based.
When we observe a child's head which is apparently malformed, we
cannot call it _abnormal_; it is not abnormal unless it has a volume
notably too small (submicrocephaly, microcephaly) or too large
(rickets, hydrocephaly); and a cephalic index exceeding the normal
limits, in other words, _exaggerated_ (scaphocephaly, trochocephaly,
pathological brachycephaly occurring in hydrocephalics).
THE VOLUME OF THE CRANIUM
The volume of the cranium owes its importance, as we have already seen,
to the fact that the cranium represents the _envelope_ of the brain,
and is consequently normally determined, as regards its dimensions, by
the cerebral volume. Accordingly, in normal cases, when we speak of
the cranial volume, we are speaking by implication of the _cerebral
volume_; and all anthropological questions regarding the volumetric
development of the cranium in reality have reference to the brain.
In abnormal cases, on the contrary, it may happen that the bony
covering is not a skeletal index of the brain; in fact, pathological
cases may occur analogous to those we have already observed in
discussing the etiology of cranial malformations, in which the flat
bones of the cranial vault undergo a notable thickening, so that as
a result the greater volume of the cranium is due to the increased
quantity of bony substance, and not of brain tissue, and is very heavy,
so that it readily droops over upon the shoulder: _pachycephalic_
cranium.
Another cause for lack of correspondence between the cerebral and the
cranial volume may be the abnormal production of cerebro-spinal fluid
within the brain: _hydrocephalic_ cranium.
=The Development of the Brain.=--In the earliest period of embryonal
life, the brain consists of a single vesicle, the continuation of
which forms the spinal marrow: later on, this vesicle divides into
three superimposed vesicles which represent respectively the embryonal
beginnings of the anterior, middle and posterior brain; continuing
their development, the anterior and posterior brains each divide
in turn into two other vesicles, so that there result in all five
primitive vesicles of the brain, superimposed one upon another (see
Fig. 75); the anterior vesicle which is destined to grow enormously,
dividing into two parts, right and left, with a longitudinal division,
will constitute the cerebral hemispheres; the second vesicle
will constitute the optic thalami; the third vesicle, the corpora
quadrigemina; the fourth vesicle, the cerebellum, and the fifth
vesicle, the medulla oblongata.
When complete development is attained, the cerebral hemispheres
completely cover the other parts of the brain, besides which they
themselves are covered over with a multiplicity of folds constituting
the _convolutions_. If we take a cross-section of the hemispheres, we
find that they consist of an outer layer of _gray_ matter formed of
nerve cells, and of a central mass of _white_ matter, formed of fibres.
[Illustration: FIG. 75. Brain of a Human Embryo after the Fourth Week.]
The study of the convolutions is quite important from the
anthropological standpoint, because their number is not identical in
the different branches of the human race, and also because they differ
both in number and in arrangement from the convolutions in the brain of
the anthropoid apes. But however interesting they may be, considered
as differentiating characteristics, we cannot linger over a study of
this kind, which has a purely theoretic importance, and for the present
cannot be applied in any practical and direct way to our problems of
pedagogic anthropology. It will be sufficient to note rapidly that at
the present time the study of the _convolutions_ has received a new
impulse through the labours of certain distinguished investigators,
among whom we must once more include Dr. Sergio Sergi. Instead of
studying the surface convolutions, Dr. Sergi studies the internal folds
which are disclosed by separating the lips of the cerebral fissures;
and from these he draws deductions which to a large extent correct
those made by previous scientists, in regard to the eventual ancestry
of the different species, the marks of biological superiority or
inferiority, the differences in the brain due to sex, etc.
The surface fissures which divide the cerebral hemispheres into
convolutions are shown in the two accompanying figures (Figs. 76 and
77), the first of which shows the outer side of the hemispheres, and
the second the inner side.
Of chief importance to us is the arrangement of convolutions and
furrows on the outer surface of the hemispheres.
The points to be noted are the following: the two great fissures,
Rolando's, running longitudinally, and Silvius's running transversely,
which, together with the perpendicular fissure, divide the hemisphere
into four lobes: the _frontal_ lobe and the _parietal_ lobe, situated
respectively in front and behind Rolando's fissure; the _temporal_
lobe, situated below Silvius's fissure, and lastly, the _occipital_
lobe at the posterior apex of the hemisphere.
[Illustration: FIG. 76.--Cerebral hemisphere; external face.]
In the third frontal convolution are situated Broca's centres, which
are believed to be the seat of articulate speech; while along Rolando's
fissure, in the ascendant convolutions, is the locality designated by
physiologists as the motor centres.
The occipital lobe is the location of the zone of sight; and the
temporal lobe, that of hearing.
It is important for us to observe the volume of the brain, and
therefore that of the head, in relation to the rest of the body; it
is enormous in the embryo; and even at birth and during childhood
the head is quite voluminous as compared with the body, as appears
from the diagram in Fig. 16, in which a new-born child and an adult
man are reduced to the same scale, each retaining his relative bodily
proportions. In Fig. 22 a new-born child is shown in two positions:
from the front and from behind; the head is very large and the cranial
nodules are plainly visible. Figs. 80 and 81 represent the same child
at the age of six months and a year and a half; in the first picture
the head is still very large as compared with the body, and the
forehead protrudes (infantile forehead); in the second, the proportion
between head and body has already altered.
A knowledge of the laws governing the growth of the brain is of
particular importance in relation to pedagogic anthropology.
[Illustration: FIG. 77.--Cerebral hemisphere, internal face.]
Within the last few years anthropologists have established certain
principles that are well worthy of notice:
1. The child's head is normal when its _volume_ and _cephalic index_
come within the limits of normality (even if the shape appears
abnormal: Simon, Binet, etc.).
2. When the volume of the head is too small it frequently indicates
psychic deficiency; when it is too large, even up to the age of twenty
years, it indicates a predisposition to precocious mortality (see
below).
Very frequently when the size of the head is larger than normal and is
not due to pathological causes (rickets, hydrocephaly, etc.), it is
associated with an excessive development of the brain, and also with
an intellectual precocity. A high percentage of this type die before
reaching the age of twenty years; and this fact confirms the popular
belief that children who are too intelligent or too good cannot live
long.
This indication alone ought to be sufficient to prove the pedagogic
importance of the cerebral volume.
The researches made by various authors in regard to the growth of the
brain are not rigorously in accord as to the _limits of volume_: but
they do agree as to the _rhythm of growth_.
Welcker gives the following figures:
WEIGHT OF THE BRAIN IN GRAMS
(According to WELCKER)
------------------------------
Age | Males | Females
------------+-------+---------
At birth | 400 | 360
Two months | 540 | 510
One year | 900 | 850
Three years | 1,080 | 1,010
Ten years | 1,360 | 1,250
Accordingly, the weight of the brain is doubled before the end of the
first year; according to Massini it is very nearly doubled at the end
of the first six months:
MASSINI'S FIGURES AS TO THE WEIGHT OF THE BRAIN
--------------------------------------------------
Age |Total weight| Increase
---------------------------+------------+---------
At birth | 352 | 68 }
First month | 420 |211 } 279
From first to third month | 631 |
From third to sixth month | 675 | 44 }
From sixth month to 1 year | 694 | 19 } 63
[Illustration: FIG. 78.--Spheroidal cranium lateral norm (Sergi's
collection).]
[Illustration: FIG. 79.--Spheroids typicus (from Sergi's collection).]
[Illustration: FIG. 80.--A child six months old.]
[Illustration: FIG. 81.--The same child a year and a half old.]
It follows from these figures that by the end of the sixth month the
weight of the brain is already very nearly doubled; but the maximum
growth takes place between the ages of one month and three, after which
it shows a notable diminution of rate.
But while the weight of the whole body is increased threefold by
the end of the first year, that of the brain is very far from being
tripled, since the rate of growth is still further diminished during
the second six months; in fact even according to Welcker the weight at
the end of the first year has little more than doubled.
Accordingly the rhythm of cerebral growth is not identical with that of
the increase in weight of the body taken as a whole.
According to Massini, the relation between the cerebral weight and the
weight of the body, at the various successive ages, is as follows:
RELATION BETWEEN WEIGHT OF BRAIN AND TOTAL WEIGHT
(According to MASSINI)
-----------------------------------------------------------
Age | Brain | Body | Age | Brain | Body
--------------------+-------+------+---------+-------+-----
At birth | 1 | 8 | 2 years | 1 | 15
First month | 1 | 9 | 3 years | 1 | 14
From first to third | | | | |
month | 1 | 9 | | |
to sixth month | 1 | 10 | | |
to one year | 1 | 12 |25 years | 1 | 40
-----------------------------------------------------------
In other words, the body grows more rapidly than the brain, and
consequently, than the head: a fact which results in the different
proportions already noted between head and body.
The rhythm of brain growth considered by itself has been set forth in
a most noteworthy and accurate fashion by Boyd, based on the study
of about two thousand cases; from the figures given by Boyd, I have
calculated the amount of increase from period to period, as well as
from year to year, the whole result being set forth in the following
table:
RHYTHM OF GROWTH OF BRAIN
(_Males_: According to BOYD)
-------------------------------------------------------------------------
|Weight|Difference|Difference| |Proportion
Age | in | for each | for each | Relative|to maximum
|grams | period | year | epoch | reduced
| | | | | to 100
-----------------------+------+----------+----------+---------+----------
At birth | 331| -- | -- | -- | 24.2
From birth to 3 months | 493| +162 | -- | -- | 36.0
From 3 to 6 months | 603| +110 | -- | -- | 44.1
From 6 months to 1 year| 777| +174 | +446 |1st year | 56.8
From 1 to 2 years | 942| +165 | +165 |2d year | 69.0
From 2 to 4 years | 1,097| +155 | +77 | 2d- 4th| 80.4
From 4 to 7 years | 1,140| +43 | +14 | 4th- 7th| 83.4
From 7 to 14 years | 1,302| +162 | +23 | 7th-14th| 95.3
From 14 to 20 years | 1,374| +72 | +12 |14th-20th| 100.5
From 20 to 30 years | 1,357| -- | -- | -- | 99.3
From 30 to 40 years | 1,366| +9 | +0.9 |30th-40th| 99.3
From 40 to 50 years | 1,352| -14 | -1.4 |40th-50th| 98.9
From 50 to 60 years | 1,343| -9 | -0.9 |50th-60th| 98.3
From 60 to 70 years | 1,315| -28 | -2.8 |60th-70th| 96.9
From 70 to 80 years | 1,289| -26 | -2.6 |70th-80th| 95.3
From 80 to 90 years | 1,284| -5 | -0.5 |80th-90th| 94.2
-------------------------------------------------------------------------
In the above table, the first column of figures gives the _mean_
_average weight_ of the brain, obtained by direct observation of
individual subjects; while from all the others the rhythm of cerebral
growth and involution throughout the successive periods of life may be
computed.
We see that the maximum growth takes place in the first years of life,
the intensity is greater in the first year than in the second, and
greater in the first three months than in those that follow. Already
at the end of the first year the brain has surpassed one-half of the
maximum weight which the individual is destined to attain in adult life
(last column: proportions computed on scale of 100). A notable rate of
increase continues up to the age of four, after which it moderates,
but receives a new impulse at about the fourteenth year (period of
puberty); hence it appears that at this important epoch of life the
_brain_ not only shares the general rapid growth of the body, but that
by the end of the fourteenth year the brain has _already practically
completed its development_; in fact, assuming that 100 represents its
complete development, the weight of the brain is already 95.3; and at
thirty it will be only 99.3.
By studying the above table we can obtain a clear analysis of these
phenomena.
For women, Boyd gives the following figures:
THE GROWTH OF THE BRAIN IN WOMEN
(Figures Given by BOYD)
--------------------------------------------------
| |Proportion to the
Age | Weight | maximum reduced
| | to 100
-----------------------+--------+-----------------
At birth | 283 | 22.8
Three months | 452 | 36.5
From 3 to 6 months | 560 | 45.2
From 6 months to 1 year| 728 | 58.8
From 1 to 2 years | 844 | 68.1
From 2 to 4 years | 991 | 80.8
From 4 to 7 years | 1,136 | 91.7
From 7 to 14 years | 1,155 | 93.3
From 14 to 20 years | 1,244 | 100.4
From 20 to 30 years | 1,238 | 100.0
From 30 to 40 years | 1,218 | 98.3
From 40 to 50 years | 1,213 | 97.9
From 50 to 60 years | 1,221 | 98.2
From 60 to 70 years | 1,207 | 97.4
From 70 to 80 years | 1,167 | 94.2
From 80 to 90 years | 1,125 | 90.8
--------------------------------------------------
The rhythm of growth of the female brain is analogous to that of the
male, except for the more precocious attainment of the maximum weight,
which corresponds to the more precocious evolution of the female
organism.
It should be noted that in the tables above cited the maximum is
actually given as occurring at the age of twenty; and that after this
period the weight diminishes again, subsequently increasing up to an
age that varies according to the sex. But this maximum at the age of
twenty must be considered as one of the false results of mean averages;
and it must be explained on the ground that after the twentieth year
the death rate has eliminated a series of individuals whose heads were
abnormally large, and that a majority of the survivors were those whose
heads had developed within normal limits.
This fact is further confirmed by Wagner's figures, cited by Broca:
MEAN WEIGHT OF THE BRAIN
(According TO WAGNER)
--------------------------------------
Age | Men | Women
--------------------+--------+--------
Under 10 years | 985 | 1,033
From 11 to 20 years | 1,465 | 1,285
From 21 to 30 years | 1,341 | 1,249
From 31 to 40 years | 1,410 | 1,262
From 41 to 50 years | 1,391 | 1,261
From 51 to 60 years | 1,341 | 1,236
Above 60 years | 1,326 | 1,203
Here again we have a false maximum at twenty, which nature subsequently
corrects through mortality.
From such knowledge we obtain certain important rules of hygiene.
The normal brain which exceeds the common limits of volume is not, in
an absolute sense, _incompatible_ with life. We need only to call to
mind certain men of genius who had the brains of a giant.
Accordingly a brain which exceeds the limits _demands of the_
_individual who possesses it_ that he shall live according to certain
special rules of hygiene. Children and young people who are _too
intelligent_, _too good_, in other words, children of the elite
class demand a special treatment, just as much as any other class
of beings that pass beyond the bounds of average normality. Parents
and teachers ought to be enlightened in regard to these scientific
principles; the growth of individuals who are exceptional in regard
to their intelligence and their emotions, should be supervised as
though it were something precious and fragile. Such individuals are
destined to be more subject than others to _infective_ _maladies_,
which frequently prove fatal, developing symptoms of meningitis and
cerebral affections. Consequently a hygienic life, _psychic repose_,
an avoidance of emotional excitement, moderate physical exercise in
farm or garden, a prolonged stay in the open country, might be the
salvation of children of this type, who often are over-praised and
over-stimulated by friends and relatives, and consequently subjected to
continual excitement and _surmenage_ to a degree destructive to their
health.
=Extreme Individual Variations of the Volume of the Brain.=--In regard
to individual variations, the authorities give various figures, from
which the following have been selected as most noteworthy for their
accuracy of research:
NORMAL EXTREMES OF INDIVIDUAL VARIATIONS IN THE VOLUME
OF THE BRAIN
-----------------------------------------------------------
| Age: from 20 to 60 years| From 60 to 90
Authors |-------------------------+-----------------------
| Maximum | Minimum | Maximum | Minimum
---------+------------+------------+------------+----------
Calori | 1,542 | 1,024 | 1,485 | 1,080
Bischoff | 1,678 | 1,069 | 1,665 | 1,080
| | | |
| _Without distinction of age_:
Broca | Maximum | Minimum
| 1,830 | 1,049
-----------------------------------------------------------
These figures refer to individuals belonging to European races.
_Comparison with the Brains of Apes._--The brain of the great
anthropoid apes (Chimpanzee, Orang-utan, Gorilla), whose total weight
of body is comparable to that of man, weighs on an average 360 grams,
and the greatest weight which it can attain is 420 gr.
_Specific Gravity of the Human Brain._--In normal individuals, the
average specific gravity is 1.03; in insane persons it is slightly
higher: 1.04.
_The Relation between the Weight of the Brain and the Cranial_
_Capacity: Figures given by Lebon_:
Weight of the brain Cranial capacity in
in grams cubic centimetres
1,450 1,650
1,350 1,550
1,250 1,450
1,150 1,350
_Figures given by Manouvrier_:
Weight of the brain Cranial capacity in
in grams cubic centimetres
1,700 1,949
1,450 1,663
1,250 1,432
1,000 1,147
=Increase in the Volume of the Brain.=--Studies regarding the growth of
the head, although not yet complete, have gone sufficiently far to give
us some useful ideas. In regard to the volume in a general sense, the
_cranium in its growth obeys the cerebral_ _rhythm_.
We shall speak in the section on _Technique_ of the methods of
measuring the head: at present it will suffice to point out that the
measurements may be made directly upon the cranium, and the _cranial
capacity_ calculated directly from the head: and that the _maximum
linear measurements_ are sufficient to indicate the volume--such
measurements being the three maximum diameters, _longitudinal_,
_transverse_, and _vertical_, and the _maximum circumference_. Even
the forehead, as an index of the general volume of the brain, is of
interest in researches relating to the volumetric growth of the head.
Regarding the growth of the several cranial dimensions, the most
accurate and complete knowledge is furnished by Binet's researches
among the school-children of Paris (1902).
This author has made special investigations into the _rhythm_ of growth
of the cranium and of the face, with special reference to the period
of _puberty_. The following are the mean averages obtained by him,
relative to the three diameters corresponding to the three maximum
dimensions of the head:
MEAN AVERAGES OF CEPHALIC MEASUREMENTS TAKEN UPON
CHILDREN OF DIFFERENT AGES
(BINET: _From the schools of Paris_)
------------------------------------------------------------------------------
| Kinder- |Lower primary schools |Upper pri- |Normal
| gartens | |mary schools|schools
|-----------+-----------------------+------------+-------
Measurement | 4 | 5 | 8 | 10 | 12 | 14 | 14 | 16 | 18
|years|years|years|years|years|years|years| years| years
---------------------+-----+-----+-----+-----+-----+-----+-----+------+------
Antero-post. diameter|169.5|173.9|174.7|177.1|181.5|181.5|185.3|188.3 | 190.4
Transverse diameter |140.6|141.7|145 |145.7|147.9|150.1|155.5|152.3 | 156.7
Vertical diameter |118.8|121.6|122 |122.8|127.6|129.7|128.1|131.4 | 130.8
-----------------------------------------------------------------------------
It is evident that these figures contain inaccuracies, especially in
regard to the vertical diameter (where the subsequent two-year period
gives a smaller measurement than the preceding) due to the fact that
the averages were obtained from an insufficient number of subjects or
from subjects differing too widely in intelligence (from schools of
different grades). For this reason Binet summarises the differences
in growth, that is, the increase in relation to the diameters, under
broad groups (six year groups, from four to ten years, and from ten
to sixteen), in order to determine whether puberty exerts a sensible
influence upon the cranial growth. The result is contained in the
following table:
INCREASE OF THE THREE MAXIMUM DIAMETERS OF THE HEAD IN
MILLIMETRES FROM FOUR TO EIGHTEEN YEARS OF AGE
---------------------------------------------------------------------------
Age in years: from -- to -- | 4-6; 6-8; 8-10 | 10-12; 12-14; 14-16 | 16-18
----------------------------+----------------+---------------------+-------
Antero-posterior diameter | 5.6; 0.8; 2.4 | 4.4; 1.8; 5 | 2.1
| \-----------/ | \------------/ |
| \/ | \/ |
| 8.8 | 11.2 |
Transverse diameter | 1.1; 3.3; 0.7 | 2.2; 3.9; 0.5 | 4.4
| \-----------/ | \------------/ |
| \/ | \/ |
| 5.1 | 6.6 |
Vertical diameter | 2.8; 0.4; 0.8 | 4.8; 2.3; 2.5 | 0.6
| \-----------/ | \------------/ |
| \/ | \/ |
| 4.0 | 9.6 |
---------------------------------------------------------------------------
From which it appears that there exists, in regard to the head, a
puberal acceleration of growth.
These conclusions of Binet are indirectly confirmed by the researches
of Vitale Vitali regarding the development of the forehead in
school-children; since it is well known that the forehead represents
the index of the general growth of the cerebral cranium.
Vitale Vitali based his observations upon school-children and students
between the ages of ten and twenty. He not only measured the width of
the forehead (_frontal diameter_; see _Technique_), but also measured
its height, obtaining the percentage of its relation to the width
(frontal index).
These are his figures:
FRONTAL INDEX AND DIAMETER ACCORDING TO AGE
(VITALE VITALI: RESEARCHES AMONG SCHOLARS AND STUDENTS
FROM 10 TO 20 YEARS OLD)
------------------------------------------
Age | Frontal | Frontal | Amount of
| index | diameter | increase
---------+----------+----------+----------
11 years | 73.05 | 107.5 | --
12 years | 74.11 | 112.0 | 4.5
13 years | 74.14 | 112.5 | 0.5
14 years | 74.80 | 114.4 | 1.9
15 years | 75.67 | 116.8 | 2.4
16 years | 77.24 | 120.1 | 3.3
17 years | 77.02 | 120.6 | 0.5
18 years | 77.36 | 121.5 | 0.9
19 years | 77.60 | 122.8 | 1.3
20 years | 77.15 | 122.1 | 0.7
------------------------------------------
Accordingly, between the years of fourteen and sixteen there is a
puberal acceleration of growth, accompanied by an elevation of the
forehead (high frontal index).
Vitali gives, as extreme limits of the frontal index, 68 and 83.
But in order to give a better illustration of the author's figures, his
own words may be quoted: "It appears from our observations that the
forehead begins to develop in notable proportions during the fourteenth
year, and that the development of the frontal region as compared with
the parietal region continues to augment up to the sixteenth year;
after this it still increases, but only by a few millimetres, until
the end of the sixteenth year. The cephalic development is completed
between the sixteenth and eighteenth years. This observed fact is of
great importance in relation to the development of the intellect."
The most complete figures at the present time on the growth of the
brain, are those of Quetelet, which follow its development from birth
until the fortieth year. They are summarised in the following table:
INCREASE IN THE CIRCUMFERENCE OF THE BRAIN AND IN ITS
THREE MAXIMUM DIAMETERS
(ACCORDING TO QUETELET)
--------------------------------------------------------------------------
| | Maximum diameters
Age |Circumference |------------------------------------------------
|in millimetres | Antero-post. | Transverse | Vertical
---------+---------------+---------------+---------------+----------------
| Men | Women | Men | Women | Men | Women | Men | Women
At birth | 335 | 335 | 120 | 120 | 100 | 100 | 80 | 80
1 year | 440 | 439 | 158 | 157 | 127 | 126 | 105 | 105
2 years | 471 | 469 | 168 | 167 | 135 | 134 | 113 | 113
3 years | 486 | 483 | 171 | 170 | 137 | 136 | 117 | 115
4 years | 496 | 493 | 174 | 173 | 138 | 137 | 119 | 116
5 years | 503 | 500 | 176 | 175 | 139 | 138 | 120 | 117
6 years | 508 | 505 | 178 | 177 | 140 | 139 | 121 | 117
7 years | 513 | 509 | 179 | 178 | 142 | 140 | 122 | 118
8 years | 519 | 512 | 180 | 179 | 143 | 141 | 123 | 118
9 years | 523 | 515 | 181 | 180 | 144 | 141 | 124 | 119
10 years | 527 | 517 | 182 | 180 | 145 | 142 | 125 | 119
11 years | 531 | 518 | 183 | 181 | 146 | 142 | 126 | 120
12 years | 535 | 519 | 184 | 181 | 147 | 143 | 127 | 121
13 years | 539 | 520 | 185 | 182 | 147 | 143 | 128 | 122
14 years | 543 | 521 | 186 | 182 | 148 | 144 | 129 | 123
15 years | 547 | 523 | 186 | 183 | 149 | 144 | 130 | 124
16 years | 551 | 525 | 187 | 183 | 150 | 145 | 130 | 125
17 years | 555 | 528 | 188 | 184 | 151 | 145 | 130 | 125
18 years | 561 | 531 | 189 | 184 | 152 | 146 | 131 | 126
19 years | 563 | 533 | 190 | 185 | 153 | 146 | 131 | 126
20 years | 564 | 535 | 191 | 185 | 153 | 147 | 131 | 126
25 years | 564 | 537 | 191 | 186 | 153 | 147 | 131 | 127
30 years | 564 | 538 | 191 | 186 | 153 | 147 | 131 | 127
40 years | 564 | 538 | 191 | 186 | 153 | 147 | 131 | 127
-------------------------------------------------------------------------
It appears from the foregoing table that after the twenty-fifth year
the growth of the cranium practically ceases in all directions. In
regard to the rhythm of growth, the problem is rendered clearer by the
following table, which gives the annual increase:
ANNUAL INCREASE IN THE MAXIMUM CRANIAL MEASUREMENTS
IN MALES
(FROM FIGURES GIVEN BY QUETELET)
---------------------------------------------------------
Age| Circumference | Antero-post. | Transverse | Vertical
| | diameter | diameter | diameter
---+---------------+--------------+------------+---------
1 | 105 | 38 | 27 | 25
2 | 31 | 10 | 8 | 8
3 | 15 | 3 | 2 | 4
4 | 10 | 3 | 1 | 2
5 | 7 | 2 | 2 | 1
6 | 5 | 2 | 1 | 1
7 | 5 | 1 | 1 | 1
8 | 6 | 1 | 1 | 1
9 | 4 | 1 | 1 | 1
10 | 4 | 1 | 1 | 1
11 | 4 | 1 | 1 | 1
12 | 4 | 1 | 1 | 1
13 | 4 | 1 | 1 | 1
14 | 4 | 1 | 1 | 1
15 | 4 | 1 | 1 | 1
16 | 4 | 1 | 1 | 1
17 | 4 | 1 | 1 | 1
18 | 4 | 1 | 1 | 1
19 | 4 | 1 | 1 | 1
20 | 1 | 1 | 1 | 1
---------------------------------------------------------
It appears from the above table that the total growth of the cranium
takes place to a notable extent during the early years of life; as
regards the diameters, the longitudinal diameter grows faster during
the first few months than the transverse; but after the first year,
the two maximum diameters which determine the cephalic index increase
in very nearly the same proportion (constancy of the cephalic index
throughout life). The vertical diameter on the contrary undergoes a
relatively much greater increase than the two others, since, although
much shorter than the transverse, it nevertheless overtakes and
surpasses it in its absolute annual increase.
This corresponds to the fact that the first two diameters are indexes
of growth relative to the base of the cranium, while the vertical
diameter is the index of expansion of the cranial vault, which more
directly follows the growth of the brain and elevates the forehead as
it pushes upward.
Quetelet's figures, however, fail to show in the rhythm of growth that
puberal acceleration which has been observed to take place in the
growth of the brain. This contradicts the researches of Vitali and also
those of Binet.
Similar studies have been made a number of times during the last few
years, especially in America, but with English tables of measurement,
and with little uniformity in the results obtained by the different
investigators.
Among the most recent and most complete figures should be cited those
of Bonnifay[38] in which however the measurement of the vertical
diameter is lacking, or in other words the third element needed, in
conjunction with the dimensions of length and breadth, to give the
volumetric factors.
CRANIAL MEASUREMENTS AT DIFFERENT AGES
(According to BONNIFAY)
--------------------------------------------------------------------------
| Absolute figures | Amount of Increase
|--------------------------+--------------------------
Age from -- to -- |Circum-| Antero- | Trans- |Circum-| Antero- | Trans-
|ference|posterior| verse |ference|posterior| verse
| | diameter|diameter| | diameter|diameter
--------------------+-------+---------+--------+-------+---------+--------
Birth to 15 days | 343.9 | 116.3 | 93.4 | -- | -- | --
15 days to 2 months| 368.7 | 126.3 | 99.1 | 24.8 | 10.0 | 5.7
3 months to 4 months| 388.8 | 132.7 | 106.0 | 20.1 | 6.4 | 6.9
6 months to 1 year | 429.8 | 145.4 | 118.2 | 41.0 | 12.7 | 12.2
1 year to 2 years| 459.7 | 154.3 | 129.3 | 29.9 | 8.9 | 11.1
2 years to 3 years| 473.5 | 161.9 | 133.3 | 13.8 | 7.6 | 4.0
3 years to 4 years| 487.4 | 166.2 | 136.3 | 13.9 | 4.3 | 3.0
4 years to 5 years| 495.7 | 169.9 | 138.3 | 8.3 | 3.7 | 2.0
5 years to 6 years| 497.8 | 171.9 | 140.4 | 2.1 | 2.0 | 2.1
6 years to 7 years| 504.4 | 172.8 | 141.1 | 6.6 | 0.9 | 0.7
7 years to 8 years| 511.6 | 175.2 | 143.7 | 7.2 | 2.4 | 2.6
8 years to 9 years| 514.1 | 176.1 | 144.3 | 2.5 | 0.9 | 0.6
9 years to 10 years| 514.7 | 176.4 | 144.2 | 0.6 | 0.3 | 0.9
10 years to 11 years| 519.8 | 177.1 | 146.6 | 5.1 | 0.7 | 2.3
11 years to 12 years| 521.1 | 177.5 | 145.7 | 1.3 | 0.4 | 0.1
12 years to 13 years| 529.7 | 180.1 | 147.8 | 8.6 | 2.6 | 1.2
13 years to 14 years| 533.1 | 178.1 | 148.5 | 3.4 | -- | 0.7
14 years to 17 years| 548.8 | 182.4 | 152.2 | 15.7 | 2.3 | 3.7
22 years to 27 years| 549.1 | 186.6 | 153.2 | 0.3 | 4.2 | 1.0
--------------------------------------------------------------------------
Among the linear measurements of the cranium, the one which serves to
give the most exact index of volume is the _maximum_ _circumference_.
This index, nevertheless, is not a perfect one, in the same sense that
the _stature_, for instance, is a perfect index in respect to the body,
because in the case of the cranium another element enters in: the
form. The cranial circumference of an extremely brachycephalic cranium
(almost circular) may contain a larger surface (and consequently
include a larger volume), than a maximum circumference of the same
identical measure, which belongs to an extremely dolichocephalic
cranium (approaching the shape of an elongated ellipse). This may be
easily understood if we imagine a loop of thread laid out in the form
of a circle: if we pull it from two opposite sides, the enclosed area
diminishes until it finally disappears as the two halves of the thread
close together, while the length of the thread itself remains unaltered.
Nevertheless, the maximum circumference still remains the linear index
best adapted to represent the _volume_; indeed, the authorities take
its proportional relation to the stature as representing the reciprocal
degree of development between head and body at the different successive
ages.
Here are the figures which Daffner gives in this connection:
DEVELOPMENT OF THE STATURE AND OF THE CEPHALIC PERIMETER
FROM BIRTH TO THE AGE OF ELEVEN YEARS
------------------------------------------------------------------------
| Males Females
--------+---------------------------------------------------------------
Number | |Stature| Cranial | Number | |Stature| Cranial
of | Age | in |perimeter,| of | Age | in |perimeter
subjects| | cms. | cms. |subjects| | cms. | cms.
--------+--------+-------+----------+--------+--------+-------+---------
65 |At birth| 51.17 | 34.58 | 65 |At birth| 50.27 | 34.23
11 | 1.55 | 74.18 | 46.74 | 10 | 1.39 | 77.20 | 46.45
30 | 2.43 | 85.32 | 48.03 | 30 | 2.45 | 83.48 | 47.23
53 | 3.34 | 91.88 | 49.20 | 49 | 3.43 | 89.97 | 47.73
112 | 4.43 | 96.64 | 49.55 | 81 | 4.50 | 96.07 | 48.37
244 | 5.42 |103.21 | 50.21 | 208 | 5.40 |100.61 | 48.76
234 | 6.41 |106.49 | 50.73 | 179 | 6.37 |104.92 | 49.87
30 | 7.30 |114.47 | 51.66 | 25 | 7.36 |117.36 | 50.38
28 | 8.38 |112.10 | 51.97 | 24 | 8.41 |121.58 | 50.72
27 | 9.40 |128.41 | 52.38 | 30 | 9.40 |126.76 | 51.10
21 | 10.34 |129.12 | 52.24 | 28 | 10.40 |130.00 | 51.08
20 | 11.42 |135.84 | 52.50 | 31 | 11.46 |137.04 | 51.42
------------------------------------------------------------------------
DEVELOPMENT OF THE STATURE AND OF THE CEPHALIC PERIMETER
BETWEEN THE YEARS OF 13 AND 22
------------------------------------------------------------
Number of subjects | Age | Stature in | Cephalic perimeter
| | centimetres| in centimetres
-------------------+-------+------------+-------------------
13 | 13.39 | 147.92 | 52.83
24 | 14.50 | 149.21 | 53.53
20 | 15.38 | 163.55 | 54.34
41 | 16.43 | 162.53 | 53.34
35 | 17.36 | 167.93 | 55.89
26 | 18.35 | 171.65 | 54.91
15 | 19.40 | 172.97 | 55.48
6 | 20.05 | 173.97 | 56.50
342 | 21.02 | 168.08 | 55.37
171 | 22.22 | 168.08 | 55.62
------------------------------------------------------------
One very important research made by Daffner is in reference to the
maximums and minimums that are normal for each successive age. This
is extremely useful for the purpose of diagnosing the _morphological
normality in relation to the age_. He naturally bases his figures
upon subjects studied by him personally, who altogether form an
aggregate number of 2,230, and are not always sufficiently numerous
when distributed according to their ages. Nevertheless, in the great
majority of groups, especially those including the younger children,
the number of subjects is sufficient and even superabundant.
At all events, Daffner's researches may serve as a valuable guide in
the researches that lay the foundation for diagnosis; and every future
investigator will find it an easier task, under such guidance, to make
his own contribution to it and to correct those inaccuracies which
(for certain epochs) are to be attributed to an insufficient number of
subjects.
Daffner distinguishes, for each year, a _maximum_ and a _minimum_ both
for the stature and for the cephalic perimeter; but since the person
having the maximum stature does not always have the maximum cephalic
perimeter, and _vice versa_, the author indicates, in connection with
the maximum and minimum figures, the other of the two measurements
which, as a matter of fact, corresponds to them in each given case.
INDIVIDUAL VARIATIONS
MAXIMUMS AND MINIMUMS OF STATURE AND OF CRANIAL
CIRCUMFERENCE