Pedagogical Anthropology

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:

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.

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.

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:

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)

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 Quétélet's figures:

CEPHALIC INDEX

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.

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).

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.

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.