450 PRINCIPAL SIR WM. TURNER ON 



which the differentiation of the lower from the upper forehead was feebly marked, 

 with the well-arched forehead of another skull, also from Queensland, in which the 

 corresponding diameter was 25 mm. In the six Scottish skulls the bregma-glabellar 

 perpendicular ranged from 16 to 24, with the mean 19 "8 mm. ; the bregma-nasal per- 

 pendicular ranged from 24 to 29 mm., with the mean 26*6 mm. 



From these measurements it will be seen that the frontal projection from the 

 bregma-glabellar chord had in the Australians the smallest mean, 18 mm. ; it was a little 

 stronger in the Tasmanians, 185, and distinctly greater in the Scottish skulls, 

 19 "8 mm. Similarly the bregma-nasal perpendicular had the smallest mean in the 

 Australians, 23 mm. ; next in dimensions in the Tasmanians, 24*3 ; and materially 

 greater in the Scottish skulls, 26*6. It should be noted that where the measurements 

 were made on skulls traced with a diagraph, they included the thickness of the bone, as 

 well as the diameter of the cranial cavity from the inner surface of the frontal to the 

 point on the chord from which the diameter was taken. Though the diagraph gave a 

 faithful outline of the contour of the cranium, it did not differentiate the proportion of 

 the perpendicular which belonged to the bone and that which appertained to the cavity. 

 As an illustration, I may state that in one of the Australian skulls through which a 

 section was made the perpendicular of the bregma-glabellar frontal arc was 16 mm., 

 the thickness of the frontal at its most projection was 11 mm., which left only 5 mm. 

 for the diameter of the cavity of the frontal arc ; whilst with the same thickness of 

 bone the perpendicular diameter of the cavity measured from the bregma-nasal chord 

 was 13 mm. By way of contrast I would cite the corresponding dimensions in a 

 Scottish skull, in which the bregma-glabellar perpendicular was also 16 mm., of which 

 the frontal bone was 6 mm. thick, leaving 10 mm. for the diameter of the frontal part 

 of the cranial cavity. The thickness of the parietal and occipital bones has also to 

 be considered in determining the length of the perpendicular, in estimating from it 

 the cerebral proportion of the parietal and occipital arcs on surface tracings made by 

 the diagraph, and in comparing these tracings with mesial sagittal sections. 



The determination of the position of the vertex, the highest point on the summit 

 of the cranial vault, has long been the subject of craniographical inquiry. Von Baer 

 measured the height from the plane of the foramen magnum to the most distant point 

 in the median line of the summit of the skull, wherever it happened to be. This 

 method was followed by Busk, # the skull being held in a horizontal plane parallel with 

 the plane of the zygomatic arches. Barnard Davis also took t the base measurement 

 from the plane of the foramen magnum. This method was for a time adopted by 

 myself and other British craniologists, and the vertex was regarded as a little behind 

 the bregma. Owing, however, to variations in the direction of this plane, Broca 

 suggested | that the anterior border of the foramen magnum, or basion, a definite fixed 



* See Busk's article in the Natural History Review, 1862, p. 352, and pi. viii. 



t Thesaurus Craniorum, p. xiv., 1867. 



I Instructions craniologiques et craniome'triques, Paris, 1885, p. 68. 



