A CONTRIBUTION TO THE STUDY OF THE SCOTTISH SKULL. 



443 



. 



108 



. 



. 147° 



. 



. 142° 



. 



120° 



. 



. 133° 





146° 30' 



# t 



149° 30' 



0. The Foramino-Basilar Angle (d). 



This angle may be taken to a certain extent as an index to the degree of slope 

 in the plane of the foramen magnum, not forgetting, however, that the variation of 

 the inclination of the basi-cranial axis will also exert an important influence in 

 modifying the size of the angle as well as variation in the slope of the above plane. 



The angle in the series of 98 skulls was found to have a range from 135° to 168°, 

 with a mean value of 147'68° ; the S.D. was 6'36 and the V. was 4'30. The following 

 values are given for the above angle in Duckworth (54) : — 



Dog . 



Cercopithecus monkey 



Simia . 



Gorilla . 



Chimpanzee . 



Aboriginals of Australia (average of 2) 



Europeans (average of 2) 



According to Duckworth there is some doubt as to the importance to be attached 

 to the angle, and that it is to be used " in comparisons of the Hominidse and Simiidse 

 with other families and other orders rather than for the comparative study of various 

 members within the limits of these families." 



While the mean value of the angle in the series of 98 skulls is just one degree 

 greater than the mean angle of two Australian specimens, the latter are too few in 

 number to warrant a conclusion as to its importance, and the same applies to the 

 European value derived from two skulls. The angle in the Scottish series includes 

 in its range the values given for the Cercopithecus monkey and for Simia. 



. According to Turner (2) the angle presents considerable variations in different 

 crania. In a Fuegian he found it lowest in value, i.e. 138° ; it reached its maximum 

 in an Australian, 157° ; while in three Australians it ranged from 139° to 157°. These 

 values are all included in the range of variation exhibited by the Scottish series. 



If we consider the spheno-ethmoidal angle as described above as comparable with 

 the orbito-basilar angle denned by Cleland. then, the mean spheno-ethmoidal angle 

 being greater than the mean foramino-basilar angle to the extent of about 5°, the 

 mean cranial curve in the Scottish series would be less than 180° by that amount, 

 and would approach the lowest value found for adult Europeans, according to this 

 author. It would seem, however, that the angles above mentioned can hardly be 

 regarded as strictly comparable. 



If we accept the value of the spheno-ethmoidal angle obtained by following 



Turner's directions as comparable with the above angle of Cleland, then the two 



mean angles, foramino-basilar and spheno-ethmoidal, would be equal, the anterior 



base would be parallel to the posterior base, and the cranial curve would be 180°. 



It seems somewhat anomalous that, while the cranial flexure of a skull which has 

 TRANS. ROY. SOC. EDIN., VOL. LI, PART II (NO. 9). 62 



