THE NASO-ORBITO-ALVEOLAR INDEX

A NEW CRANIOMETRIC METHOD, INCLUDING A DESCRIPTION OF A

SPECIALLY DESIGNED INDEXOMETER FOR ESTIMATING IT

JOHN CAMERON Professor of Anatomy, Dalhousie University, Halifax, N . S.

The author has been engaged for some time on a comparative study of measurements of the facial portion of the skull, and after some ex- perimenting has been able to secure results that appear worthy of being placed on record. He made a preliminary communication on the subject to the Royal Society of Canada in May, 1919, and since then was privileged to study the collection of crania in the Royal College of Surgeons Museum, London, England, during the summer of 1919, thanks to the kindness and courtesy of Dr. Arthur Keith. These investigations inspired the production of a specially designed indexometer, the description of which is now published for the first time. I can find no evidence of this “naso-orbito-alveolar” method having been previously utilized in craniometry.

All the investigations recorded in this memoir were conducted on adult male crania, the reason for this being that the orbital contours were found to vary with age and sex throughout all the racial types, where this comparison could be made. As the lower orbital margins were utilized for one of the horizontal planes in the research, it was therefore found essential to confine the study to one sex. As soon as a representative collection of female racial types can be secured, it is intended to carry out an independent investigation on these, along lines similar to those followed in this research.

Crania of the following races were examined: European, Ancient Egyptian, Hindoo, Chinese, Eskimo, Polynesian, North American Indian, Ancient Inca, Patagonian, African negro, Melanesian, aborigi- nal Tasmanian, and aboriginal Australian. I was also enabled, through the courtesy of the Bureau of American Ethnology, to utilize the photographic reproductions of the Muniz collection of ancient Inca crania in the 16th Annual Report of the Bureau of American Ethnology, and the plates in HrdliEka’s memoir on the Lenape In- dians (Bull. 62, Bur. Amer. Ethn.).

63 AMER. JOUR. PHYS. ANTHROP., VOL. 111. No. 1.

64 JOHN CAMERON

Several of the well-known types of fossil Horninids were also utilized in this research. I have never had the privilege of studying the actual specimens in the case of the Obercassel Cro-magnon man, the “old man” of Cro-magnon, the LaChapelle cranium or the Grimaldi re- mains, though I have frequently seen the Gibraltar Skull in the Royal College of Surgeons Museum. I was, however, enabled to apply my method to photographic reproductions of these taken from the works of Bonnet,’ Boule2 and Verneau3 and from the plates illustrating HrdliEka’s memoir on types of fossil Hominids. (“The Most Ancient Skeletal Remains of Man,” 2 ed., 8”.

The naso-orbito-alveolar index may be calculated in two ways: (1) by drawing certain lines on photographs of the skulls, or (2) by using the author’s specially designed indexometer (Fig. 1).

In regard to the photographic method, it was essential that the orientation of the skulls should be exactly the same in all cases, and it was found most convenient to use the Frankfort plane. One im- portant point to be noted was that the relative levels of the camera and the skull had to be the same for each series of crania. The simplest way to ensure this was by focusing the midpoint between the nasion and the akanthion (point of nasal spine) on to the intersection of diagonal lines drawn on the ground glass screen of the camera. Hori- zontal lines were then drawn through the following four points on each photograph-the nasion, the lower orbital margins, the akanthion and the alveolar point. Two vertical lines were then drawn along the outer margins of the nasal aperture. It will be noted that three of the cranial points chosen possess a fair degree of positional constancy, and it may be further observed that the plan makes full use of the re- markably constant and trustworthy nasal index. It may be mentioned here that in the case of the LaChapelle skull a small piece of bone is absent from the region of the nasion, thus rendering the localization of this point only approximate. The horizontal line drawn through the lower borders of the orbits does not possess so high a degree of constancy as the others. Moreover, i t was found that in some of the skulls the lower orbital margins were not on the same horizontal plane, in which case the mean of these was taken.

When these lines were drawn in the manner indicated, the result was an elongated rectangle, with the long sides placed vertically, and subdivided into three subsidiary rectangular areas (see the illustra-

Smiths. Inst., 1916.)

1 Die Naturwissenschuften, 1914, Heft. 27. 2 Ezt. Annul. Puhont., VI, VII and VIII. a Les Grottes de Grimddi. Monaco, 1906.

THE NASO-ORBITO-ALVEOLAR INDEX 65

tive figs.). It will, therefore, be recognized that the index is really composite in character, for one can calculate the relationship of the width to the height of the complete rectangle, or to the height of each of the subsidiary rectangles, and this is the plan that has been adopted.

It is to be particularly noted that all the measurements recorded were made on the photographic reproductions. It is essential that this fact should be mentioned, as it is obvious that in a very prog- nathous skull the nasion-alveolar point height would be decidedly less than the total aggregate of the nasion-akanthion and the akan- thion-alveolar heights. In compiling the indices it was decided to follow the plan of estimating the nasal index. The nasal width, which formed the foundation of the whole scheme, was therefore multiplied by 100, the result being then divided by the height of each rectangle in turn.

The second method of estimating the naso-orbito-alveolar index is by means of the author’s specially designed Indexometer, of which a brief description will now be given. It possesses the merit of being readily made a t home and of being easily applied. All that is required is the possession of two long and four shorter pieces of thin, stout wire, which are arranged in the manner shown in Fig. 1. At each inter- section a thinner piece of wire is twisted lightly round both, but sufficiently firm to make the apparatus hold together and yet permit of the horizontal pieces of wire being moved up or down, and the verti- cal pieces in a lateral direction. I am endeavouring t o make arrange- ments with a scientific instrument maker to manufacture a suitable model of the indexometer which will possess a double sliding joint of the close fitting tubular type a t each intersection of the wires.

Mode of Application.-The indexometer is placed against the skull so that the uppermost bar rests against the nasion and the lowermost bar against the alveolar point. The lower ends of the upright wires of course rest upon the table and they require to be slid towards or away from each other, until each lies exactly anterior t o the outer border of the nasal aperture. The intermediate horizontal bars are then moved up or down as the case may be until they lie exactly anterior to the lower orbital margins and the akanthion respectively. It is of course clear that the uppermost and lowermost bars are the only ones that are in actual contact with the skull. A little practice enables one to become proficient in the application of the indexometer. The relation of the nasal width to the height of the complete rectangle or to the height of each of the subsidiary rectangles can then be readily estimated, as explained previously.

66 JOHN CAMERON

On investigating the results yielded by this composite index in the male crania of the various racial types enumerated above, it was ascer- tained that it divided races into two great groups. The first group comprised the European, ancient Egyptian, Hindoo, Chinese, Eskimo, Polynesian, North American Indian, ancient Inca and Patagonian

FIG. 1. A sketch of the author’s naso-orbito-alveolar Indexometer. It consists of two vertical and four horizontal pieces of stout wire with a double sliding joint at:the eight intersections, so as to admit of the horizontal pieces of wire being moved up or down and the vertical pieces in a lateral direction. For its mode of applica- tion see the text.

THE NASO-ORBITO-ALVEOLAR INDEX 67

racial types, while the second group, which might be termed the negro group, included the African negro, aboriginal Australian, aborigi- nal Tasmanian and Melanesian racial types. In the first group the height of the uppermost rectangle was always greater than its width, its index being therefore well under 100, while the two lower rectangles approximated closely to the outlines of squares, their in- dices being somewhere in the neighbourhood of 100, sometimes above

FIG. 2. Represents European and Ancient Egyptian types of skull. It is to be noted how closely the relative proportions of the three horizontal dotted areas of the facial skeleton correspond to each other in these two racial types. It is to be observed further that the two lower rectangles in each case are approximately squares, while the uppermost rectangle is elongated vertically.

and in other cases below. Moreover, the index for the complete rect- angle, that is to say, the relation of the nasal width to the nasion- alveolar height, was as a rule under 40. In the Eskimo skull in my collection this index was found to be as low as 31.6 owing to the con- traction of the nasal width.

In the second or Negro group, on the other hand, the upper two rectangles approximated to the outlines of squares, their indices being somewhere round 100; while the lowermost rectangle, owing to the great reduction in its height due to the prognathism in these races, exhibited an index of at least 192.5 (African negro), indicating of course that the nasal width was practically twice the height of t he

68 JOHN CAMERON

lowermost rectangle. In an aboriginal Australian cranium the index for this rectangle was as high as 252.5. Moreover, the index for the complete rectangle in these races was always well over 40, that is to say, the nasal width was in all cases more than 40 per cent of the naso- alveolar height. In an aboriginal Australian skull it was as high as 50.7 per cent. It is therefore manifest that this index demarcated races into two definite groups,l the appearance exhibited by the various rectangles being illustrated in Figs. 2, 3, 4 and 5 .

I n Fig. 2 European and ancient Egyptain types of skull have been placed side by side in order to demonstrate how closely the relative proportions of the three horizontal areas of the facial skeleton corre- spond in these two racial types. Note further that the two lower rectangles in each case are approximately squares, with indices there- fore in the vicinity of 100, while the uppermost rectangle is elongated vertically, with an index well under 100 in both crania. The writer has previously referred more than once2 to the high type of index that is exhibited in some ancient Egyptian skulls, and is therefore not surprised to find that the naso-orbito-alveolar index consistently follows these, and brings the two racial types into some degree of approximation.

I have placed the Mongolian, Polynesian and Eskimo types to- gether in Fig. 3. It will be observed once more that the relative pro- portions of the three horizontal areas of the face and the outlines of the three rectangles correspond more or less closely to those in Fig. 2, except in the case of the Chinese cranium. I utilized the latter deliberately as an example of variation, since two other skulls of this race that I examined showed relative proportions of the three rect- angles that conformed to the European-Asiatic type. This variation is due to the varying levels of the lower orbital margins which would of course affect the relative proportions of the uppermost and inter- mediate rectangles. The degree of variation of the naso-orbito- alveolar index cannot of course be fully worked out until a large series of crania has been examined. In the meantime I will have to rest satisfied with the demonstration and mode of application of the index.

I had difficulty in deciding where to place the Eskimo skull in the illustrative Figs. for this paper. As he has some Mongolian attributes,

1 The zone of demarcation between these groups would become greatly reduced in an extensive series of crania.

* Manchester University Museum Publication, No. 68, 1910; also Trans. Nova Scotian Inst. Sci., XIV, Pt. 1, 1916.

THE NASO-ORBITO-ALVEOLAR INDEX 69

I placed him with the Chinese and Polynesian crania. Owing to his contracted nasal aperture, however, he occupies a definitely isolated plane, and I have therefore installed him in the upper part of Fig. 3 by himself.

FIG. 3. Shows Chinese, Polynesian and Eskimo types of skull. The rectangles of the Eskimo and Polynesian types of crania correspond more or less to those de- picted in Fig. 2. The Chinese cranium has been utilized to demonstrate the fact that the naso-orbito-alveolar index has a considerable range of variation.

70 JOHN CAMERON

Representatives of three aboriginal races of the Western Hemisphere have been chosen for Fig. 4, which demonstrates that the relative proportions both of the three horizontal dotted areas of the facial

FIG. 4. Representation of the crania of three aboriginal races of the Western Hemisphere. There is a certain degree of correspondence in the relative heights of the three rectangles, which makes them conform more or less to the European- Asiatic type. The nasion-alveolar height of the Patagonian skull is an unusual feature, though apparently not a definite character of this race.

THE NASO-ORBITO-ALVEOLAR INDEX 71

FIG. 5. Shows that African negro, aboriginal Tasmanian, aboriginal Australian and Melanesian types of skulls give corresponding results when studied by means of this index. The two upper rectangles are approximately squares, while the lower- most show an extreme degree of reduction of their heights, due of course to the prog- nathism in these races. These crania thus display a marked contrast to those of the Euro-Asiatic type.

72 J O H N CAMERON

skeleton and of the three rectangles conform more or less to the general European-Asiatic form, or what might be termed the Eurasiatic type. I was much struck by the amount of the nasion-alveolar point height in the Patagonian skull. An examination of this cranial group in the Royal College of Surgeons Museum, however, demonstrated the fact that this did not appear to be a characteristic racial feature.

The inter-racial range of variation in the relative sizes of the three rectangles was such that the Eurasiatic races, the Polynesians and the aborigines of the Western Hemisphere were practically on the same level. Thus it appears as if the Eurasiatic tfpes-could be linked by this craniometric method with both the American Aborigines and the Polynesians. In a previous communication’ the writer has referred to the fact that the crania of the aborigines of the Western Hemisphere betray some Mongoloid affinities, and a link with the yellow-brown Mongol of Asia is also provided by the Polynesians of the Pacific. I n reference to this fact it is important to quote HrdliEka’s remarks on p. 183 of Bulletin No. 52 of the Bureau of American Ethnology2: “This general American type is more or less related to that of the yellow-brown peoples, wherever these are found without decided ad- mixture with other strains. These yellow-brown people, including the American, represent one great stream of humanity.”

Fig. 5 demonstrates the fact that the naso-orbito-alveolar index placed the African negro, the aboriginal Tasmanian, the aboriginal Australian and the Melanesian on the same plane. It is interesting to note how the uppermost and intermediate rectangles approximate in all four cases to the outlines of squares, and are therefore about equal in size, their indices being somewhere in the vicinity of 100. The great feature of Fig. 5 is, however, the great reduction in the height of the lowermost rectangle, due, as previously explained, to the high degree of prognathism in these races. The index for it was there- fore about 200 or even much more (192.5 in the African negro, 199.9 in the aboriginal Tasmanian, 234.5 in the Melanesian and as high as 252.5 in an aboriginal Australian), indicating of course that its height was about one half its breadth-in some cases much less.

T H E CRANIA O F FOSSIL H O M I N I D B

On comparing Fig. 5 with Fig. 6 , it is evident that the cranium of the Grimaldi youth exhibited fairly consistently the characteristics of

1 Trans. Nova Swtian Instit. Sci., Vol. XV, Pt. 1, 1919. * Early Man in South America, 8O, 1912. See also his “Genesis of The American

Indian,” Proc. XIX Intern. Cong. Amer., Wash., 1917.

THE NASO-ORBITO-ALVEOLAR INDEX 73

J

FIG. 6 . Tracings of the Grimaldi slcull (Verneau), the Obercassel skull (Bonnet), and the La Chapelle cranium (Bode).

The Grimaldi skull shows the Negro type index. In the Obercassel specimen the index conforms fairly with that of the Euro-Asiatic type. The Cro-Magnon race represents the only example of fossil Hominidae amongst those examined that could with safety be placed in the Eurasiatic category. In the La Chapelle skull it will be observed that the three rectangles are quite different from those of the racial types represented in Figs. 2 to 5.

74 JOHN CAMERON

the negro naso-orbito-alveolar index. He could therefore be definitely placed in his appropriate racial position. The indices for the upper- most and intermediate rectangles of his skull were approximately 100, while that for his lowermost rectangle was found to be as high as 233.3-that is to say, practically the same as that for the modern Melanesian skull cited in the preceding paragraph.

The skulls of the Obercassel Cro-magnon man (Fig. 6b) and of the “old man” of Cro-magnon, were the only cranial types of fossil Hominidze amongst those examined that could be safely placed in the Eurasiatic category. A study of Fig. 6b will demonstrate the fact that the relative proportions of the three horizontal dotted areas of the Obercassel facial skeleton conform more or less to those of the general European-Asiatic type, while the indices for the three rect- angles likewise consistently follow this result.

The application of the naso-orbito-alveolar index to the La Chapelle and Gibralter crania, representing Neanderthal-Mousterian man, provided some interesting results. The great nasal width of these two crania seemed at first sight to render them comparable, to those of the modern negro type, but the height of the lowermost rectangle in both instances at once negatived this impression (Fig. 6c) . On examining this figure it will be noted that the three horizontal dotted areas of the La Chapelle skull were almost equal in height, which rendered it quite different from the modern European-Asiatic type or the modern negro type. Moreover the three rectangles were also quite different from those of the modern racial types, for all three were approximately equal in size and were transversely elongated owing to the great nasal width. It is thus clear that the Neanderthal- Mousterian type of skull is one that does not exist a t the present day.

ENUMERATION OF THE VARIOUS MODES OF APPLICATION O F THE NASO-

ORBITO-ALVEOLAR INDEX

1. Calculate the relation of the nasal width to the height of the complete rectangle, that is to say, the relation of the nasal width to the nasion-alveolar height.

2. Calculate the relation of the nasal width to the height of each of the three subsidiary rectangles.

3. Calculate the relation of the square area of the three subsidiary rectangles to each other. For this investigation the crania would all have to be photographed to the same scale of reduction. 4. The relative proportions of the three horizontal areas of the

a F

IG. 7.

T

he n

aso-

orbi

to-a

lveo

lar

met

hod

is s

een

to d

ivid

e ra

ces

into

two

dist

inct

gro

ups.

T

he sk

ulls

wer

e al

l red

uced

to

the

sam

e si

ze

appr

oxim

atel

y.

76 JOHN CAMERON

facial skeleton mapped out in Figs. 2 to 6 could be studied. This investigation might be regarded as accessory to the estimation of the naso-orbito-alveolar index, and so far as I have been enabled to de- termine, promises to provide a new and fruitful field of research.

In concluding this paper which is to be regarded entirely as a pre- liminary announcement owing to the comparatively small series of crania examined, and the vast issues that have been introduced, I wish to emphasize the fact that all the conclusions arrived at have been based entirely on this one ‘ I naso-orbito-alveolar” craniometric method. It is quite obvious that one cannot depend upon it alone as a means of classifying mankind. Still, its value as a further means of studying the cranium appears to present certain possibilities. Another reason for this publication is that it may stimulate further study of the comparatively neglected norrna f r o n t a h of the skull.