Pedagogical Anthropology

by Maria Montessori

The Cranium

The Head and Cranium.—Let us bear in mind the fact that the word head is used in speaking of a living person, and cranium, of a skeleton.

The science which makes a study of the cranium is called craniology. The cranium and the head may be studied either by observing the external form—cranioscopy or cephaloscopy; or else by taking measurements—craniometry or cephalometry. Craniology makes use equally of cranioscopy and of craniometry: in fact, if cranioscopy alone were used, certain anomalies might escape attention, because we can recognise them only by measuring the head; and conversely, if we confined ourselves to craniometric researches, we might miss certain anomalies of form, which we become aware of only by attentively observing the cranium. Frequently craniometry serves to verify cranioscopy. For example, a cranium may appear to the eye too large or too small, but certainly if we measure the cranial circumference with a tape-measure we shall have an accurate decision of a case which may well be a simple optical illusion. Indeed, we all know how easy it is to give an erroneous judgment, relying only on our senses; for the personal equation enters very largely into judgments of this sort. For instance, a person of low stature easily judges that other men are tall, and vice versa. To the eye of the Italian or the Frenchman, the hair of young English girls is a pale blond; to the Scandinavians of the North it is a warm blond. If two men possessed of different æsthetic tastes and in different frames of mind wish to describe one and the same garden they will give two widely different descriptions which will reveal far more of their individual impressions and moods than of the actual characteristics of the garden described. It is easy to understand how important it is in scientific descriptions to exclude completely the influence of the observer's personality. In the cranioscopic study of a cranium, for instance, the precise characteristics of that cranium are what must be found and nothing else whatever, no matter who the student is nor in what part of the world he is working. But in order to achieve this result it is not enough to take observations; it is also necessary to know how to observe, and in observing to follow a scientific method.

Cranioscopy.—Cranioscopic methods require that the skull shall be observed from several sides. Blumenbach, who studied crania by observing them from the vertex, divided them into ovoid, rhomboid, etc., while Camper, on the other hand, studying them in profile, classified them as flat, elongated, etc., and the conclusions of the two scientists were irreconcilable.

Fig. 146.—Facial norm.

Fig. 147.—Occipital norm.

Fig. 148.—Lateral norm.

The cranium must be observed from above, from the front, in profile and from the occipital part; and in such a manner that the observer's glance shall fall perpendicularly upon whichever cranial side is under observation. Hence it is said that the observation is made according to the norm, i.e., according to the perpendicular, and there are four norms in cranioscopy—vertical, frontal, lateral, and occipital. In this way we may be sure that no anomaly of form will escape the eye.

There are innumerable anomalies of form. We will indicate only the principal ones. In order to detect all the anomalies that may occur in a cranium it is necessary to observe it according to all the norms, each one of which may reveal a different set of anomalies.

A. Vertical Norm.—The word norm, as we have already said, has here the signification of perpendicular. To look at a cranium according to the vertical norm means to let our glance fall perpendicularly upon the vertex of the cranium. We may do this in one of two ways, either by raising our head above that of the subject of inspection, in such a way that our glance falls vertically upon it, or by bending back the head of the person to be observed until the crown of his head becomes perpendicular to our gaze. This norm is taken by placing oneself behind the person to be observed, who, if an adult, should be seated while the observer remains standing; and by taking the head to be examined between the two hands in such a way that the extended thumbs and index-fingers form a horizontal circlet around the cranial walls.

This is the most important of the norms, not only because it reveals the most important normal forms already described in the text, but also the greater number of anomalies such as are indicated below.

1. Crania with Rectilinear Perimeter.—It may happen that the line bounding the cranial vault is not curved but formed of broken straight lines from which various geometrical figures result, producing crania known as trigonocephalic, pentagonoid, parallelopipedoid, etc.

The most important among these and among all the abnormal forms is the trigonocephalic cranium, having the base of the triangle toward the occiput and the vertex toward the forehead. The result of such formation is that the frontal region is restricted, a circumstance of obvious gravity. The infantile cranium is normally pentagonoid; the persistence of this form in the adult is a sign of arrested development, but not serious. Sergi does not admit this form among the anomalies when the nodules are but slightly emphasised.

2. Asymmetrical and Plagiocephalic Crania.—The sagittal plane divides the cranium into two unequal halves. The asymmetry may be either frontal, in which case one frontal nodule is more prominent than the other—anterior plagiocephaly, or else parietal, in which case one of the parietal nodules is more prominent than the other—posterior plagiocephaly.

These are the two forms of simple plagiocephaly. It may happen that there is simultaneously an anterior and posterior asymmetry, and in such a case it generally happens that if the more prominent frontal nodule is on the right, the more prominent parietal nodule is on the left, so that the two more prominent nodules correspond in a diagonal sense. This is compound plagiocephaly.

Plagiocephaly is extremely common; if very apparent, it constitutes a grave defect, but not if only slight. For that matter, it would be difficult to find a cranium rigorously symmetrical, even among normal persons.

3. Crania with curved and symmetrical lines, but in which the perimeter consists not of a single ellipsoidal curve, but of two curves.

a. Clinocephalic Cranium.—The coronal suture has a girdle-like furrow, in such fashion that there result an anterior and a posterior curve which together form a sort of figure 8. This anomaly may be perceived also from the lateral norm.

b. Cymbocephalic Cranium.—- There is a girdle-like furrow along the sagittal line, so that the cranium has the appearance of being divided into two pockets, one on the right hand and the other on the left.

B. Lateral Norm.—The observer must stand at the side of the subject to be observed and look at him perpendicularly to the profile.

We remain standing while we look if the subject is an adult and is standing up, but we sit down if the subject is a child and is standing; and we determine the vertical position by moving the subject's head as the occasion requires.

I note, as seen from this norm, two anomalies in which the ellipsoidal uniformity outlining the profile of the cranium is altered.

a. Oxycephalic Cranium.—The line of the profile is noticeably raised at the bregma, from which the anterior part of the cranium continues to rise, almost in the direction of the forehead, instead of curving backward. In its entirety this anomalous cranium has the form of a "sugar loaf."

b. Acrocephalic Cranium.—The line of the profile, on the contrary, is not raised until near the lambda.

C. Occipital Norm.—The observer places himself behind the subject and gazes perpendicularly at the occipital point.

D. Frontal Norm.—The observer stands in front of the subject and gazes at him on a level with the forehead.

I may point out only one very important anomaly seen from this norm.

a. Scaphocephalic Cranium.—The lateral parts of the cranium are flattened to such a degree that the vault is extremely narrow along the sagittal line (see Figs. 51 and 52).

Craniometry.—The volume of the cranium is of high importance because it bears a relation to that of the brain. In the studies which have been made relative to the correspondence between physical and intellectual development, the measurement of the cranial volume comes first in order.

In measuring the cranium it is necessary to use:

a. the millimetric tape measure, b. the craniometric calipers, c. the compass with sliding branches, d. the double square. In order to facilitate the task of measuring and to secure uniformity it is necessary first to locate the craniometric points to which it will be necessary to apply the instrument. These craniometric points are easily located on the cranium, where a great number of them have been studied. In the case of a living person, on the contrary, these points are reduced to a small number because of the difficulty of accurately locating them.

The points on the vault of the cranium, along the sagittal line, are:

1. The nasion (point of union of the nasal and frontal bones).
2. The ophryon (middle point of the line tangent to the two superciliary arches, a line corresponding to the horizontal drawn transversely across the forehead and passing through the two points on the temporal lines which are nearest to the median line. This point lies in an important region of the forehead, situated between the two eyebrows—the glabella. The central point of the middle region of the forehead above the glabella is called the metopion).
3. The bregma (point of juncture between the coronal and sagittal suture).
4. The vertex.
5. The lambda (point of juncture between the sagittal suture and the occipital or lambdoid suture).
6. The occipital point.
7. The inion (situated at a level midway between the occipital point and the occipital foramen).

Laterally we have these other craniometric points:

1. The external orbital apophysis (formed from the frontal bone).
2. The supra-auricular point.
3. The auricular point (corresponding to a little depression which may be felt just below the tragus and in correspondence with the zygomatic arches).
4. The minimum frontal point (a bony angle which may be felt about 1 centimetre above the external orbital apophysis, along the temporal line).

On a living person the following points can easily be located:

Along the sagittal line:

1. The nasion.
2. The ophryon.
3. The vertex.
4. The occipital point.

Laterally:

1. The external orbital apophysis.
2. The supra-auricular point.
3. The auricular point.
4. The minimum frontal point.

Now, with these points as guides it becomes practical to measure the various curves and diameters of the cranium. The curves are measured by means of the millimetric tape; the diameters by means of the calipers.

There are various curves; we shall confine ourselves to considering only the following:

The maximum circumference, which is obtained by passing the tape across the ophryon, the occipital points and the supra-auricular points, beginning to apply it at the ophryon. Its measure varies from 520 to 540 mm. in man and from 490 to 510 mm. in woman, if taken from the skull. In the case of a living person 20 mm. should be added.

If we find a circumference greater than normal, we are beginning to enter upon the anomaly which goes by the name of macrocephaly. If, on the other hand, the maximum circumference is notably smaller, we are entering upon the anomaly of microcephaly.

Measurement of Diameters.—Maximum Antero-posterior Diameter.—With the left hand place one branch of the calipers upon the glabella; the other extreme point is to be sought tentatively along a vertical line dividing the occiput in two halves. Partially close the calipers by means of the screw and then make trial by raising and lowering the posterior branch. It ought to move with a slight friction.

This is the classic diameter which measures the maximum length of the cranium and which, as we have seen, it is customary to compare with the width in order to obtain the cephalic index. In the adult man it normally oscillates between 170 and 180 mm.

Fig. 149.—Inspecting cranium (lateral and vertical norms).

Maximum Transverse Diameter.—This measures the width of the cranium. The investigator places himself in front of the subject in order to keep the compass quite horizontal through the guidance of the eyes. The maximum distance is found by experimenting. It normally corresponds very nearly to the supra-auricular points. In children this diameter is frequently situated higher up toward the parietal nodules; in men of tall stature, in whom the cranial vault is generally slightly developed, this diameter may be found, on the contrary, lower down, near the mastoid apophyses. If this diameter occurs similarly low down in children, a notable growth in stature may be prophesied (Manouvrier); and if inquiry is made it will be found that the parents are very tall. This diameter measures, in the adult, from 140 to 150 mm.

Vertical Diameter.—This measures the height of the cranium from the occipital foramen to the bregma. This diameter cannot be measured directly excepting on a skull; in the case of a living person its projection is taken, which, though far from accurate, is given by the distance between the vertex and the external auditory meatus.

It is necessary to use the double square. The horizontal branch is placed tangent to the vertex, its direction should be perceptibly parallel to the transverse orbital line, the graduated vertical branch should pass over the auricular foramen. The required number may be read, corresponding to the point of the tragus.

The height of the cranium is exceedingly important; its variations produce variations in the physiognomy.

In the first period of childhood, the cranium is very low in comparison to its width; this is also true of dwarfs. In these cases the width of the cranial vault is large in comparison to that of the base; a low cranium bulging above is distinctive of babies and dwarfs.

In the adult this diameter measures from 130 to 140 mm.

Among the other measurements which an taken on the cranium, the following may be cited:

The antero-posterior metopic diameter: from the metopic to the occipital point. In children it is sometimes the maximum longitudinal diameter.

The ophryo-iniac diameter from the ophryon to the inion.

The minimum frontal diameter: between the two minimum frontal points.

The maximum frontal diameter: between the two external orbital apophyses.

The bistephanic diameter: between the two stephanic points.

The bitemporal diameter: this is the greatest width of the cranium between the verticals passing through the base of the tragus.

The biauricular diameter: the craniometrical points are in front of, and a little below, but very near to the upper insertion of the auricle. They are little depressions that can be felt, as we have already said, by applying the finger along the upper edge of the root of the zygomatic arch.

Height of forehead: from the ophryon to the roots of the hair.

Circumferences and Curves:

Anterior Semicircle.—The tape is applied from one supra-auricular point to the other, passing through the ophryon; it corresponds to the anterior part of the maximum circumference. Manouvrier measures it in correspondence to the verticals erected from the tragus.

Posterior Semicircle.—This is obtained by subtracting the anterior semicircle from the whole circumference.

Vertical Curve of the Head.—The tape passes through a plane that is vertical to the orientated head, starting from the supra-auricular points or from the tragus, according to different authorities.

Cephalic Index.—This is the proportion between the maximum transverse and longitudinal diameters. It is obtained by applying the familiar formula:

Ci = (100×d)/(D)

in which d represents the transverse diameter and D the longitudinal. The index represents the percentual relation between the two diameters, and is obtained from the formula by reducing the greater diameter to a scale of 100, as follows:

D:100 = d:X, whence X = 100×d/D

Instead of working out the calculations, we may find the required index in the tables already compiled.

Volume.—The volume of the cranium cannot be taken directly, except in the case of a skull. After the various osseous foramina have been closed, the cranial cavity is filled through the occipital foramen with any one of a number of substances (millet, shot, water, etc.), which is afterward measured. The method of taking this measurement is practised on a facsimile of a cranium already calculated, and usually made of metal.

But in the case of a living person the direct calculation of the volume is impossible. Nevertheless various empirical methods have been sought for obtaining this measurement, even though imperfect and approximate. Recently renewed use has been made, especially in France, of an approximate calculation made by means of Broca's cubic index. The volume of the cranium is equal to half the product of the three diameters, divided by an index which varies according to age.

This index is as follows:

Adults from 25 years upward.	men	1.20
	women	1.15
Young persons from 25 to 20 years.	men	1.15
	women	1.10
Young persons from 20 to 16 years.	men	1.10
	women	1.08
Children of both sexes.	15-10 years	1.07
10-5 years	1.06
5 years and below	1.05

An index of cranial development is afforded by the maximum circumference. The average volume of the normal adult cranium is about 1,500 cubic centimetres: mesocephalic cranium.

When the cranium is much inferior in volume, it is called microcephalic (from 1,200 down to 700 cubic centimetres). When on the contrary it is much superior (from 1,900 up to 2,200 cubic centimetres), it is called macrocephalic or megalocephalic.

For the face, the following craniometric points should be noted:

Along a longitudinal line:

1. The nasion (point of meeting of the nasal and frontal bones).
2. Subnasal point (meeting of nasal septum with upper maxilla).
3. Upper alveolar point (between the two upper incisors at their point of insertion).
4. Lower alveolar point (point corresponding to the above, in the lower maxilla).
5. Mental point (middle point of the chin).
6. The following craniometric points are situated laterally.
7. Auricular point (corresponding to the auricular foramen; in living persons it is situated on the tragus).
8. Malar point (on the malar bones).
9. Zygomatic point (corresponding to the zygomatic arches).
10. Gonion or goniac point (angle of mandible).

The face also may be studied by inspection—prosoposcopy; and by measurement—prosopometry.

Prosoposcopy.—We proceed to inspection according to two norms: A. facial norm; B. lateral norm or norm of profile.

A. Facial Norm.—If it is a question of a living person, we make complete inspection of the visage, from the roots of the hair to the chin. First of all we direct attention to the forehead, which will give us an index of the development of the anterior region of the brain; next, we observe whether a plane passing longitudinally through the median line would divide the face into two equal halves (facial symmetry).

From an æsthetic point of view, the three following vertical distances ought to correspond in length:

Height of forehead (from the roots of the hair to the nasion).

Length of nose (from the nasion to the subnasal point).

Labio-mental height (from the subnasal point to the point of the chin). And in regard to width the three following horizontal distances ought, according to the æsthetic laws of art, very nearly to correspond (especially in the female face):

Width of forehead, between the two external orbital points.

Bimalar width, between the two malar points.

Bigoniac width, between the two gonia.

It should be remembered that the standards of beauty do not necessarily coincide with those of normality.

B. Lateral Norm.—In observing the face according to this norm, three facts should be chiefly noted:

1. The relative volumetric development between facial and cerebral cranium.
2. The direction of the forehead, which, in the normal profile, ought to be vertical.
3. Whether the facial profile protrudes or not beyond the extreme anterior limit of the forehead.

Prosopometry.—-Many forms of measurements are taken on the skeleton of the face and many total and partial indices are obtained, such, for instance, as the facial index, the orbital index, the nasal index, etc.

Measurements of diameters and angles are also taken on the face of the living subject and indices are obtained.

We, however, shall limit ourselves to indicating only those measurements which are taken most frequently in our special field of application.

The diameters and the height of the face are obtained by the craniometric calipers and Mathieu's compass with sliding branches; the facial angle is measured in projection by means of the double square; and directly, by the goniometer.

One mode of measuring the facial angle in projection is that of drawing the facial profile with the help of special instruments; or else of taking a photograph in perfect profile and tracing and measuring the facial angle on the picture.

Principal Linear Measurements:

Total length of visage: from line of hair root to point of chin.

Total length of face: from the nasion to the point of the chin.

Length of the nose: from the nasion to the subnasal point.

Height of mandible: from the upper edge of the lower incisors to the lower edge of mandible.

Subnase-mental height: from the subnasal point to the point of the chin.

Bizygomatic diameter: between the two bizygomatic arches.

Bimalar diameter: between the two malar points.

Bigoniac diameter: between the two gonia.

Biorbital diameter: between the two external borders of the orbits.

Gonio-mental distance: from the goniac point to the point of the chin.

Auriculo-frontal radius: from the tragus or from the auricular point to the ophryon.

Auriculo-subnasal radius.

Auriculo-mental radius.

(The last four measurements, if compared right and left, give an index of facial symmetry; the radii when compared together serve as an indirect measure of prognathism.)

Width of nose between the external borders of the nostrils (the branches of Mathieu's compass are placed tangent to the nostrils).

(The index of the nose is obtained from the length and breadth, by applying the well-known formula of indices; the nose thereupon receives various names—leptorrhine, mesorrhine, platyrrhine).

Width of orbit: from the inner extremity of the ocular rima (eye-slit) to the external border of the orbit.

Width of the ocular rima: between the two extremities of the rima.

Width of the labial rima: between the two extremities of the rima.

Length of the ear: from the highest upper edge of the auricle to the lower extremity of the lobule.

Index of the ear: this is obtained, by the well-known formula, from the length and breadth. The normal index is 50; the types of ear above 50 are low types.

Anthropologists obtain the facial index from the skeleton, especially for the purpose of determining the proportion of the face in human remains found in the geological strata. In such crania the mandible is wanting, and the teeth are wanting. Consequently, there are several ways of computing the facial index, because, while the transverse or bizygomatic diameter, which is considered as the lesser diameter, always remains constant, the longitudinal, which is considered as the greater, varies. The longitudinal diameter is calculated sometimes from the ophryon to the chin, at others from the ophryon to the point of insertion of the two upper middle incisors. In the first case it is now less, and again greater than the bizygomatic diameter; in the second case, it is always less, and the resulting facial index is notably greater than 100.

The most usual formula for the facial index is the following:

Fi = (bizygomatic diameter×100)/(ophryo-mental diameter)

on the basis of which Pruner Bey gives the following mean averages according to race, for the general facial index:

Arabs	96.7
Chinese	101.7
Hottentots	105.7
Tasmanians	109.9
Laplanders	124.7

This index is not exact and constant, like that for the cranium; in fact, in case a person loses his teeth the index is altered. At the present day, especially in the French school, the anterior or total facial index is taken into consideration, in which the vertical diameter is measured from the vertex of the head to the chin (Collignon), and, consequently, the index is always less than 100. The following is the nomenclature that results for the anterior facial index:

Leptoprosopics	62 and below
Mesoprosopics	from 62 to 66
Chameprosopics	66 and above

If we take for the measure of length that of the visage, i.e., the distance between the middle point of the frontal line of roots of the hair and the chin, we obtain indices that are higher by 5 than those of the French school, namely:

Leptoprosopics	67 and below
Mesoprosopics	from 67 to 71
Chameprosopics	71 and above

In many cases this index differs in the individual by as much as 10 from the cranial index, as I proved in my work on the population of Latium. Consequently, anyone who has a cranial index of 81 ought to have a visage index of 71, etc.

Contrary to what happens in the case of the cranium, the index of the face varies according to the age, the face being very short in childhood, and much longer in the adult.

Angles.—The angles distinguished by anthropologists are so numerous that it is impossible for us to take them all under consideration.

In the case of a living person, the angles may be measured directly with the aid of Broca's goniometer; the transverse branch passes across the subnasal point; the two antero-posterior branches are inserted, with the buttons with which they terminate, into the external auricular canals; the vertical branch, swinging on a hinge, is adjusted in such a way that the little rod which it carries at the end rests upon the ophryon.

This complicated instrument resembles an instrument of torture and could not be applied to children; furthermore, it is difficult to adjust, and consequently the angles that it gives are inexact: every muscular contraction causes the angle to vary. For this reason the goniometer is impracticable.

If, by means of an instrument we trace the projection of the facial profile, the facial angle may be taken on such a drawing; it may also be traced and calculated on a photograph taken in profile.

Broca's angle is that included between the auricular foramen, the subnasal point and the ophryon.

Camper's angle is that included between the auricular foramen, the point of insertion of the upper incisors and the metopic point.

We, on the contrary, in judging of the facial angle, or rather of the existence and degree of prognathism, have resorted to inspection, aided by certain facial lines, namely (Fig. 104):

a. Vertical Facial Line.—If the subject holds his head level, with the occipital point in contact with a vertical rod, and his gaze fixed straight before him, then what we call the vertical line is the line perpendicular to the horizontal direction of the gaze, and tangent to the extreme anterior limit of the brain. This line, in the perfect human face, is perpendicular to the horizontal line uniting the auricular point with the subnasal point, and hence forms a right angle with it.

b. Line of Facial Profile.—This is the line uniting the nasal point with the subnasal point. This line is never vertical, and therefore cannot form a right angle with the auriculo-subnasal line, but forms an angle that approximates more or less nearly to a right angle (85°): this is the facial angle.

Transversely there is only one line for us to consider, and it has already been noted:

c. The auriculo-subnasal line, or line of orientation.

Facial Norm.—Our attention should be directed, as we have already said:

1. To the forehead.

This, if anomalous, may be:

• Broad (if greater than 133 mm.).
• Narrow (if less than 100 mm.).
• High (if over 60 mm.).
• Low (if under 50 mm.).

2. To the Symmetry of the Face.—If the face is notably asymmetrical, in respect to a plane dividing it longitudinally, the fact is at once perceptible. But a slight asymmetry may fail to be detected either by measurements (trago-mental diameters) or by inspection. Consequently, it will be well to follow certain practical rules in making this observation.

Observe first of all the median line of the face: the bridge of the nose, the nasal septum, the upper labial furrow and the point of the chin ought all to lie in the same vertical line; very often a slight deviation of the nasal septum above the upper labial furrow will betray the asymmetry; furthermore, the two naso-labial plicæ or folds should be noted, for they ought to be symmetrical in direction and in depth; lastly, we must observe the symmetry of the zygomatic prominences. We shall often discover three concurrent facts: a slight deviation in the median line of the face usually corresponding to the nasal septum; a greater depth of one of the naso-labial plicæ; and a greater prominence of the zygoma and the cheek on the same side.

Our attention should next be turned to the correspondence required by æsthetics between the following three diameters:

• Minimum frontal.
• Bizygomatic.
• Bigoniac.

A very notable difference between these distances may also lead to the discovery of anomalies.

Sometimes we may discover, even by inspection alone, a notable narrowness of the frontal diameter, as compared with the other two.

The bizygomatic diameter may show an exaggerated development, and this is frequently accompanied by a hollowness in the temporal and upper maxillary regions and by a beak-like prognathism (prominence of the middle portion of the upper maxilla); at other times this degenerative sign calls our attention to the mongoloid type.

The bigoniac diameter may also show an exaggerated development due to the enormous volume of the mandible (criminaloid type—Lombroso's assassin type). It is necessary to supplement our observation with the measurement of these three diameters, because it may very often appear to the eye that the minimum frontal diameter is below the normal, merely by comparison with the other two diameters which are overdeveloped; while when measured, it may turn out to be normal. Or, conversely, the other diameters, the bizygomatic or bigoniac, although actually normal, may appear overdeveloped, because of the shortness of the minimum frontal diameter (see "Faces of Inferior Type.")

Meanwhile we must not forget that the following are signs of grave degeneration:

a. The minimum frontal diameter less than 100 mm. (the gravity of this is increased if at the same time the other two diameters are found as described in b).

b. The other two diameters greater than 110 mm. (Lombroso's born delinquents, assassin type).

Lateral Norm, or Norm of Profile.—Our attention ought to be directed, as we have already said:

1. To the direction of the forehead. If abnormal, this may be:

• a. Receding;
• b. Bombé.

The receding forehead is an indication of an incomplete or defective development of the frontal lobe of the brain; we find the forehead notably receding in the microcephalic type.

The bombé forehead is characteristic of hydrocephaly, but may occur also in the scaphoid cranium. When the forehead is bombé, the facial angle becomes equal to or greater than a right angle, because the face recedes beneath the extreme anterior boundary of the brain; in this case we have the opposite case to prothognathism, namely, orthognathism.

2. Our attention should next be directed to the facial profile, in order to observe the form and degree of prognathism.

The authorities distinguish three principal forms of prognathism:

a. Prognathism properly so-called: prominence of the upper maxilla as a whole.

b. Prophatnia.—Prominence of the alveoli.

c. Progeneism.—Prominence of the mandible—the lower dental arch projects in front of the upper.