CORRELATION BETWEEN THE INTERORBITAL WIDTH AND T H E NASAL WIDTH O F

T H E SKULL

CRANIOMETRIC STUDIES, No. 29

A survey of the interorbital width and the nasal width in the crania not only of man, but also of the three highest anthropoids, suggested to the author that a definite correla- tion probably existed between these two cranial dimensions. For instance, the Eskimo, as is well known, possesses the lowest average among the Hominidae for the width of the nasal aperture of his skull. The writer was therefore much interested to note that the Eskimo crania recorded also the lowest average interorbital width for all the racial types that were available for study. This observation encouraged him to continue along this path of inquiry. He therefore selected, next of all, the Hamann Museum male negro crania, which, as previously noted, presented the greatest average inter- orbital width among all the available racial types, namely, 27.15 mm. He found that the average nasal width for these crania was also relatively great, the actual figure being 27.18 mm., which, it may be noted, was almost exactly the same as that for the interorbital width. This closeness in the figures was manifested by the female Negro crania, which yielded an average interorbital width of 25.5 mm. and an average nasal width of 25.9 mm. It was also interesting to find that the Hamann Museum white crania, which exhibited an average interorbital width intermediate between those for the Eskimo and the negro crania, also presented an average nasal width intermediate between those for the Eskimo and the negro crania. Another observation which the writer made on these Hamann Museum crania is also probably worthy of being recorded. For instance, he noticed that the average

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CRANIOMETRIC STUDIES 521

interorbital width was fractionally greater than the average nasal width in the white crania, both male and female. On the other hand, the average nasal width was fractionally greater than the average interorbital width in the negro crania, both male and female. These results will be found recorded in table 1.

This correlation between these two cranial dimensions WRS

also well exemplified by the Mongol crania. Thus their aver- age interorbital width was 25.4 mm., which was definitely higher than that recorded by the Eskimo crania. Their nasal width followed these results consistently by displaying an average dimension likewise higher than that for the Eskimo crania, namely, 27.5 mm.

The correlations found in the three highest anthropoids were also of interest. Thus the gorilla skulls, which yielded the greatest average interorbital width, also furnished the greatest average for the nasal width, while the orang skulls, with a very low average for the interorbital width, displayed also a low average for the nasal width. This correlation between these two cranial dimensions was also shown by the chimpanzee skulls. It was thus interesting to note that the correlation between these two cranial dimensions which existed in the human skull also held good for the three highest anthropoids (table 1).

A brief discussion on these correlations will suffice. I n the first place, it should be noted that a considerable proportion of the interorbital width is made up from the upper portions of the right and left nasal fossae, as they extend upward toward their roofs. One would therefore conclude that ex- treme interorbital widths would mean unusually capacious nasal fossae with their associated air sinuses. Again, one would also conclude that abnormally wide nasal apertures would mean increased capacity of the lower portions of the nasal fossae. I n this way, therefore, increased interorbital width and increased width of the nasal aperture of the skull become naturally interrelated. The writer should add that, on the other hand, a reduction in the width of the nasal aper-

522 JOHN CAMERON

ture does not necessarily always mean a diminution in the capacity of the nasal fossae. Observations which he has made in the crania of various racial types prove the correctness of this observation. Of course, a reduction in the interorbital width would assuredly be expected to produce a diminution in the capacity of the upper portions of the nasal fossae.

TABLE 1

A correlation exists between the average interorbital width and the average dimensions of the nasal aperture of the skull, both in the Hominidae and in

the three highest anthropoids. That is to say, an increased interorbital width is associated with an increased nmal width, and vice versa

Interorbital width, mm.

Male Greenland Eskimo (U. S. Natl. Museum), 21.7 Female white (Hamann Museum), 23.3 Male white (Hamann Museum), 24.6 Male Mongol (U. S. Natl. Museum), 25.4 Female negro (Hamann Museum), 25.5 Male negro ( Hamann Museum), 27.15

Width of nasal aperture, mm.

22.9 23.1 23.8 27.5 25.9 27.18

Gorilla (Hamann Museurn), Chimpanzee (Hamann Museum), Orang ( Hamann Museum),

32.9 37.2 24.4 29.4 15.5 24.9

In view of the facts just recorded, i t was evident that the mathematical calculation of these correlations was justifiable. The author accordingly decided to utilize the Hamann Museum white and negro crania and the Eskimo crania for the necessary calculations. The correlations could not be cal- culated in the cases of the other racial groups, on account of the small numbers of crania represented.

The coefficient of correlation in the case of the Hamann Museum male white crania was found to be +0.6518, a result which indicated, of course, a favorable degree of correlation. The probable error of this coefficient of correlation was cal- culated to be +0.05007. The result yielded by the Hamann Museum male negroes was not quite so good, the actual coefficient of correlation being +0.5264, with a probable error of k0.06295. The writer expected to find a highly favorable coefficient of correlation in the case of the male Eskimo crania, which one would naturally look for in a comparatively homogeneous race. Their coefficient of correlation was, how-

CRANIOMETRIC STUDIES 523

ever, only f0.1859, with a probable error of k0.02757. This low degree of correlation may be explained to some extent by the small number of Eskimo crania that were available, namely, thirty ; that is l o say, exactly one-half of the numbers examined in the other two racial groups. I n calculating the coefficient of correlation for these Eskimo crania, the total yielded by the +zy column was only 43.75, while the total of the -zy column amounted to 25.25. This meant, of course, a very narrow margin of difference for the production of a really favorable correlation.

CONCLUSIONS

1. The author found that a correlation existed between the interorbital width and the dimensions of the nasal aperture of the skull, both in the Hominidae and the highest anthro- poid apes. That is to say, an increased iiiterorbital width was associated with an increased nasal width, and vice versa.

2. Among the racial types that were available, the coeffi- cient of correlation was found to be $0.6518 for the Hamann Museum male white crania, +0.5264 for the Hamann Museum male negro crania, and +0.1859 for the Greenland Eskimo male crania.