CRANIOMETRIC STUDIES JOHN CAMERON

Dalhousie Uninersif>r, Halifax, N. S.

NO. 1. THE CORRELATION BETWEEN THE NASION-BASION LENGTH AND

THE MAXIMUM GLABELLA-OCCIPITAL LENGTH The series of craniometric studies of which this is the first has only

been rendered possible through the courtesy and kindness of my friend, Professor T. Wingate Todd, who granted me permission to examine the unique collection of human crania in the Harnann Museum, Western Reserve University. In addition to free access to the required material I had also the ever present help and cooperation of Professor Todd and his staff, particularly in connection with the working out of the very num- erous and, in many instances, coinplicated mathematical formulae in- volved in the calculations. It was a real pleasure to be able to work under such advantageous conditions, and I wish to place on record my keen sense of appreciation of many kindnesses.

The crania examined were those of adults, representing all ages from 26 to 83. In the present research the collection has been examined in groups for each sex and each race, but it is hoped in later researches to organize these into decades in order to ascertain the existence of age changes, if any.

It is important to mention that no skull was examined until i t had be- come perfectly dry. Professor Todd fixes for each skull a definite date, previous to which the drying of the bone cannot be said to be complete. In this way any risk of subsequent shrinkage is eliminated as much as possible.

I may state that the Hamann collection of human osteological nia- terial is unique, the name, sex, age, and, in most cases, the race of every skeleton in the collection being known and kept carefully recorded. There is indeed nothing else like it in the world to-day. The number of complete skeletons was over 1200 when I was there (JClay, June, 1924) and the collection is expanding with great rapidity every year.

For my particular research the only crania applicable were those that had been sectioned in the sagittal plane. I found 602 thus treated, and was able to examine these in the most advantageous way.

The object of the present cranioinetric study was to ascertain from this wealth of material whether or not there was any correlation betmeen the nasion-basion length and the maximum glabella-occipital length. The writer can find no record of this having been done previously.

143 . b r . J . PHYS. ANTHROP., 1928. Vol. VII I , KO. 2 .

144 JOHN CAMERON

The crania were divided into four groups-male White, male Negro, female White and female Negro. Three crania had afterwards to be excluded from the list owing to defect or previous damage, and the final numbers reported upon consisted of 358 male White, 153 male Negro, 51 female White and 37 female Negro-599 crania in all. The extensive series of male white crania represented nationalities from every country or district in Europe, and this was vividly exemplified in the amazingly diverse types met with in this group.

It may be stated at the very outset that a very definite correlation was found to exist between the above two cranial lengths.

The nasion-basion length varied from a maximum of 107 mm. to a minimum of 87 mm. in the female Negroes, from 109.5 mm. to 91 mm. in the male Negroes, from 105 mm. to 85.5 mm. in the female Whites, and from 110.5 mm. to 87 mm. in the male Whites. It will be noted from this list that the degree of racial variation was practically the same in the females of both races-only 0.5 mm. of a difference; but the variation was much greater in the male Whites than in the male Negroes.

The glabella-occipital length varied from a maximum of 192.5mm. to a minimum of 169 mm. in the female Negroes, from 206.5 mm. to 168 mm. in the male Negroes, from 193 mm. to 161.5 mm. in the female Whites, and from the extreme limits of 210 mm. to 160.5 mm. in the male Whites. I t will be observed that the variation was, as in the case of the nasion-basion length, by far the greatest in the male White crania, an amazing divergence of 49.5 mm. It seems incredible that this cranial length should exhibit such an excessive range of variation.

FEMALE NEGROES

A. Basion-nasion Length: The mean was found to be 95.9 mm. and the error of the mean was

calculated to be ~ 0 . 4 7 9 mm. The standard deviation was 4.32 mm., the error of which was found to be 10.339 mm. The coefficient of variation proved to be 4.5y0 and the error of this was &0.353%.

B. Maximurn Glabella-occipital length: The mean was lS0 mm:, the error of the mean, by applying the usual

formula, being ~ 0 . 6 1 5 mm. The standard deviation, 5.55 mm., was expected to be slightly higher than in the case of the nasion-basion measurement, owing to the greater cranial length involved. The error of standard deviation was 0.435 mm., the coefficient of variation 3.08%, and its error 0.241%.

CRANIOMETRIC STUDIES 145

MALE NEGROES

A. The izasion-basion length: The mean of this was 100.5 mm. The error of the mean proved to be

~ 0 . 2 3 3 mm. The standard deviation, 4.27 mm., was very nearly the same as that of the female Negroes, and the same statement applied to the coefficient of variation, 4.25%. The error of the standard deviation was +0.165 mm. and that of the coefficient of variation ~ 0 . 1 6 4 7 ~ . The closeness of these figures is quite remarkable.

B. The Maximum Glabella-occipital length: The mean was 186 mm., and its error ~ 0 . 3 2 7 nim. The standard de-

ation, 5.99 mm., and the coefficient of variation, 3.22y0, were both closely similar to the corresponding results in the female Negro crania. The error of the standard deviation was calculated to be =t0.231 mm. and that of the coefficient of variation =t0.124%.

FEMALE WHITES

A . The nasion-basion length: The mean was 94.8 mm., and its error ~ 0 . 4 2 5 mm. The standard

deviation, 4.51 mm., was slightly higher than in both the female and the male Negroes, while the coefficient of variation, 4.75y0, was likewise more unfavourable than in both the female and the male Negroes. The error of the standard deviation was ascertained to be ~ 0 . 3 0 1 mm., and that of the coefficient of variation ~0.318%.

B. The Maximum Glabella-occipital length: The mean was 174 mm. and its error =t 0.711 mm. The standard

deviation, 7.54 mm., was decidedly more unfavourable than in both the male and female Negro crania, while the coefficient of variation, 4.32y0, followed this result consistently, and proved to be worse than in both the male and female Negro material. The error of the standard devia- tion proved to be =t0.502 nm. and that of the coefficient of variation ~0 .288%.

MALE WHITES

A. The izasion-basioit length: The mean was 100 mm. and its error dl.156 mm. The standard

deviation, 4.39 mm., was greater then in both the male and female Negro crania, while the coefficient of variation, 4.39Oj,, was more unfavourable than in the case of the male Negroes. The error of the standard devi- ation was =t0.1103 mm., and that of the coefficient of variation =t0.1103%.

140 JOHN CAMERON

.B. The ~iZa~::'~~:~t:z glabella-occipitcl le?.ig;li: The mean was 1S2 imn. and its error &0.-383 iiiiii. The standard

deviation, 7.98 inin., was nearly the same as in the female White crania, and was much more unfavourahle than in both the inale and female Negro inaterial. The coeficient of variation, 4.3Ss,, Tq-as almost the same as that of the female Whites and much n-orse than in both the male and female N e p o crania. The error of the standard deviation was fouiid to be = t O . X O C , inn. and that of the coefficient of variation

The ov.tstanding fact elicited by these results is, that the .American ATegro crania, both male and female, are more stable than the nlale and female White crania, as regards both the standard deviat,ion and the co- efficient of variation. This would suggest that the American Negro is racially more homogeneous than the American White. One can well iiiiagiiie the ama7ing diversity of White represented by a y e a t iiiiddle west city like Cleveland, which is uiidoubtedly one cf the great racial melting pots of the United States. I am interested to find that these conclusioix are coi$%-niatory of those obtained by Professor Wingate Tcdd' as the result of a comparison of various cranial measurements in the same iiiaterial that I have utilized. Ke mas likewise much im- pressed by the stability of the A'egro material, when cciiirared u-ith the relative wuiability of the results yielded by the crania of the Wii te races. For example he states? that-"Ccmparing the inale series, there is somewhat less variability in our IVegroes than in our Whites except in the case of auricular height. Probably this greater variability of the Whites is related to the markedly heterogeneous character of the White population." Again in the next paragraph he states-"The absence of any correlation between length and breadth in our male White crania together with the approximately similar correlation of these two dinien- sions with capacity still further indicate mixed character. Contrast this situation with the condition in the male Negroes. In the latter there is much greater correlation of both length and breadth with capacity and there is fair correlation between length and breadth them- selves. "

* 0 . 1 1 0 1 ~ .

CORRELATION B E T W E E N NASION-BASION LENGTH -4ND THE MAXIMUM

G LAB ELLA-OCCIPITAL LENGTH

It will be useful to mention here how this correlatioii is calculated. For each skull the deviation froin the mean of the nasion-basion length

'Cranial Capacity and linear dimensions in White and Negro. Am. J . Phys. Antlzrop., 1923, VI. No. 2.

2op. cit., 16.5.

CRAXIOMETRIC STUDIES 147

is multiplied by the deviation from the mean of the glabella-occipital length. If both deviations be + or - the result will of course be +, but if One deviation be + and the other-, the result will be-. The + and - ColUliliIS are added up separately and the totals subtracted. The f column should of course yield by far the larger total in order to obtain a favourable correlation. The result of this subtraction is then divided by a denominator obtained by multiplying together the number of crania. the standard de.-iation of the nasion-basior, length and the standard deT.-iation of the glabella-occipital length. Perfection of positive correlaticil is represented by + 1, so that one ought to get a result as near this fig.ure as possible in order to prove definitely if there is really any correlation. A minus result of course means that there is inverse correlation. The most pronounced correlation was found in the female White crania where the result mas + 0.65. The next best re- sult, +0 .4 i4 i1 was obt,aiiied in the male Negroes. The figure for the inale Vfhite crania i x i s +0.44G and for the female Negroes +0.3563. The errors of the coefficients of correlation were 10.054, 10.042, 10.02s and 4.9% respectively.

I caiinot close this coniixunication without expressing my gratitude to Professor Wingate Todd, Miss Lindala, Miss Kuenzel and Miss Trenkel of the Departnient of Anatomy, Western Reserve University, and my colleague, Professor J. H. L. Johnstone, for indispensable assistance in checking many thousands of calculations.

TABLE I. THE NASION-BASION LEKGTII. Mean Standard Deviation Coefiicient of

Variation Female Negroes. . . . . . . , 95.9rt0.479 4.321t0.339 4.5 10.353 Male Negroes. . . . . . . . . . 100.5+0.233 4.27k0.165 4.25 +0.164 Female Whites. . . . . . . . . 94.8rt0.42.5 4.51 10.301 4.75+0.318 Male Whites. . . . . . . . . . . 100. 1t0.156 4.39 It0.1103 4.39&0.1103

Note the close approximation of the mean in the females and males of both races. The standard deviatim and the coefficient of variation will both be observed to be consistently higher in ihe M-hite races.

TABLE 11. THE hfAXIMUM GLABELLA-OCCIPITAL LENGTH. Mean Standard Deviation Coefficient of

Variation Female n’egroes. . . . . . . . 1SOrt0.615 5.55&0.435 3.08 f0.241 Male Negroes. . . . . . . . . . 18610.327 5.99 10.231 3.221t0.124 Female Whites. . . . . . . . . 1741t0.711 7.541t0.502 4.32+0.288 Male Whites. . . . . . . . . . . 152&0.283 7.9810.2006 4.39&0.1103

Note that the standard deviation and the coefficient of variation consistently follow the results obtained for the nasion-basion length-being decidedly higher in the White crania both male and female. The close correspondence of the Standard Deviation and the Coefficient of Variation in the White and in the Negro sexual groups is remarkable.