# Popular Science Monthly/Volume 5/May 1874/Measures of Mental Capacity

Layout 4
* MEASURES OF MENTAL CAPACITY.
By J. W. REDFIELD, M. D.
SCIENCE cannot look otherwise than favorably upon every attempt to determine the quantitative relations of mind and body; and much ingenuity has been expended in the effort to arrive at a geometrical expression of it. Aristotle, "the father of Natural History," as Prof. Agassiz calls him, speaks of an angle of the forehead to an horizontal line of the face as an indication of intelligence, and it is evident that the Greek sculptors designedly represented the superhuman attributes of the gods by an angle exceeding that of the highest human. It is not strange, therefore, that, when Camper restored the lost science and art of the measurement of psychological development, under the name of the Facial Angle, in 1784, the scientific world gave it a cordial welcome. But of course it could not be accepted as veritable scientific truth without running the gantlet of the severest criticism. Its most vulnerable point was a claim to be something more than a mere general rule, applicable to the designation of the rank of a species or of a race in the scale of intellectual and moral elevation. It claimed to be applicable to the distinction between nationalities, and even between individuals of the same class of society, both as to facial and as to mental characteristics. This was too much, and on this ground Blumenbach and others attempted to demolish it as a rule altogether, and by very many were supposed to have succeeded. Like other favorites, it had the misfortune to be made too much of, the consequence being that it came to be treated as of little worth. And yet nearly all comparative anatomists and physiologists make use of it as a ​general measure of the position of a vertebrate species in the scale of cerebral and mental development. As a mere "general rule," to which, as is familiarly said, "there are always exceptions," it is certainly invulnerable, and is too valuable to be dispensed with. Hence, naturalists, while declaring it to be unreliable, have made a general application of it to the species of vertebrates, and to the races of mankind. Not only so—they have attempted to find out the definite grains of allowance in its application to particular cases, to discover the corresponding defects in the instrument, and to correct, improve, and perfect it. May it not be that the mistake is not so much in the facial angle as in the misunderstanding of its significance? If this can be shown, naturalists and ethnologists ought to make haste to receive the much-honored and much-abused facial angle into more hearty favor than ever.
But it will hardly do to proceed to this pleasant task before stopping to notice the proposition of the article entitled "The Facial Angle," in the March number of The Popular Science Monthly, to replace Camper's facial angle by another and better. The writer repudiates the angle of the frontal line with the base-line of the face, and proposes to supersede it by an angle of the frontal line with the axis of the body. He says, what everybody will admit, that the frontal line of the face is on a line with the axis of the body or spined column, in the lowest vertebrates, and that the two lines are parallel with each other in man. The absurdity of finding a facial angle, or any other angle, between two parallel lines, is evident at a glance. It might take two or three glances, but no more, to convince the ordinary mind that those two lines, with the cerebrum and cerebellum between them, cannot come in contact with each other, and can therefore form no angle between them, even in the lower animals. Disregarding the interposition of the brain, and extending the front line of the face and the axial line of the body, in imagination, until they meet, the intersected angle is not facial, and in the anthropoids it is so high in the air overhead as to be essentially visionary. Perhaps this is the reason why we have to look in vain at the only facial angles represented in the article referred to, Figs. 2 and 3, to find an illustration of the new facial angle proposed, concluding finally that they were intended to illustrate the old one. The truth is, supposing the brain to unite, instead of separate, the frontal line of the face and the axial line of the body, the bending of the continuous right line formed by them in the lowest vertebrate fishes into the two parallel lines in man, the one facio-abdominal and the other occipito-dorsal, is not by angles at all, but by curvatures, and the union of the parallels is by an arch over the head. The arc in each case is a greater or less part of a circle, according to the grade of intellectual and moral development. For example: In the typical man, the facial and dorsal lines, being parallel and perpendicular, are united at the top by a semicircle, very nearly ​describing "the dome of thought, the temple of the soul." In the gorilla, the same lines, being inclined to each other, are united by about a quarter of a circle, nearly circumscribing the cranial and mental capacity of that venerable progenitor of ours. In the goat, the same lines, being still more inclined, are united by about an eighth of a circle, giving verge and room enough for his caprices. And so on to the least part of a circle, representing the least cerebral and mental capacity.
The rule of comparison here indicated will apply perfectly to each one of the ten profiles illustrating the scale of development in the principal figure of the article in question; but that artificial angle of the frontal line of the face to the dorsal line of the body will not apply at all to intelligent human beings, except in the case of the Flatheads, whose peculiar conformation has been produced by a too rigid application of it in their plastic infancy. In man as Nature made him, the front line of the facial angle can form an angular relation to the axis of the body through the base-line of the facial angle, and in no other way. At the top of the head the front and dorsal lines can only meet in a curve, and there they form what may more properly be called the cranial arch than the facial angle. The facial angle of Camper is truly an angle and truly facial, but the proposed substitute for it is neither. Nature really does form angles of varying acuteness and obtuseness to the base-line of the face at its two extremities—very acute angles between it and the front line of the face at its anterior extremity, and very obtuse angles between it and the line of the spinal column at its posterior extremity, in the lower vertebrates, and almost right angles at the same points in human beings. Those formed by the front and base lines of the face constitute the facial angle of the upper part of the face, and indicate the degrees of intellectual and artistic development: those formed by the base-line of the face and the axial line of the neck constitute the facial angle of the lower part of the face, and indicate the degrees of affectional and passional development.
To do full justice to the article we have stopped to consider, we must not slight the assertion on which the author bases his objection to Camper's facial angle and his preference for his own, namely, that "the base of the skull does not keep in harmony" with the front of the face in the changes that occur through the stages of vertebrate evolution, but that it "varies irregularly," while the "axis of the body" does not. A little examination will show this to be a great mistake. While the lines representing the front face and dorsal surfaces are "effecting a grand variation of 180°, or the half of a circle"—beginning with the lowest vertebrate, in which those lines are "in direct line" with each other, and ending with the highest vertebrate, in which they are parallel with each other—the line representing the base of the face, extending along the floor of the ​nostril to the occipital condyle, remains stationary. While the upper jaw maintains its fixed position, the lower jaw plays upon it; and so, while the base-line of the face in the upper jaw remains steadfast, the lines based and dependent upon it—the front facial line above, and the axial line below—are each effecting variations of 90° in relation to it, the one in relation to its anterior extremity and upper surface, and the other in relation to its posterior extremity and under surface, passing on the way through the angles represented in a b, Fig. 1, and ending as represented in a b, Fig. 2—the two variations together constituting
| Fig. 1. | Fig. 2. |
| Degrees of the Superior and Inferior Facial Angles. ||
the variation of 180°, or the half-orbit before mentioned. The base-line of the skull, so far from "varying irregularly," varies not at all, but is always straight, and in the most natural position of the head is always horizontal, while the frontal line of the face and the dorsal line of the body diverge more and more from the horizontal, and become more and more irregular in figure. The position of the head natural to social intercourse and to an outlook upon the horizon, as the general rule, is the one thing in which not only all men, but all vertebrate animals, are agreed, but they take infinite liberty to disagree in all other things, for the sake of showing the infinite diversity of individualities necessary to their harmonious interrelations and to the perfect individuality of the whole. When a man's "head is level," he is on a plane of equality, as a man and an animal, not only with his fellow-men, but with his fellow-creatures, and in a position to harmonize his differences with theirs. This horizontal position of the base-line of the face makes it the standard by which to compare the other lines, and by which to estimate the degrees of intelligence and affection as indicated by the degrees of the angles they make with it. When we consider how irregular in position and contour the spine and the features of the face become in the course of transition from the ​lowest vertebrate forms to the highest, we see the absurdity of making either of these lines the basis of an angle in relation to the other. Take the novel rule, that for the true facial angle "the relation of the [front] face is not to the base of the skull, but to the axis of the body," and, for example, apply it to the camel! What sort of work would we make in deciphering such a hieroglyphical facial angle as that? But, considering the invariable straightness of the base of the skull, and its horizontal position in the attitude of attention, or in the social exercise of the external and internal senses and emotions, and considering at the same time the infinite variety of forms and motions given by these faculties to the features and muscles of the face and to the spinal column and its appendages, we see the propriety of making the base-line the standard of comparison for the two other lines in the construction of our facial angles and in our method of using them. All things considered, we may plant ourselves anew on the base-line of the old facial angle, assured that it is what its name signifies—fundamental, the centre of support and dependence between the transitional and variable lines, and presenting fixed extremities, constituting axial centres, in relation to which the movable lines are radii, forming with the baseline angles of all degrees between one and ninety in the development of animal life, from the lowest vertebrate form up to its highest and most perfect type. No one can read Camper's work "On the Connection between the Science of Anatomy and the Arts of Drawing, Painting, and Statuary," and examine its numerous and scrupulously accurate illustrations, without being convinced that the facial angle there described is founded in Nature, in spite of all the criticisms he or others may be able to pass upon it. If it be true, as Herbert Spencer says, that science is distinguished from common knowledge by being a more accurate system of measurements of ordinary phenomena, guided by more accurately understood and applied principles of generalization, Camper's facial angle may be regarded as the first step of a strictly scientific mind in the erection of a positive science of Comparative Physico-Psychology; and we have only to learn its true significance better than the master, by following the same induction of generals in regard to each particular line of it that he followed in regard to the whole, in order to complete the magnificent superstructure for which he laid so solid a foundation.