Chapter II: Craniology (1)

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.

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.)

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 bombé_), 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.

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.

=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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

=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.

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 (Rütimeyer, von Höller, 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 = 100×d/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