446 



Dli MATTHEW YOUNG. 





There is a distinct interval between the index shown by the human skull in its 

 various types and that of the various anthropoids, which have always an index well 

 above 50, usually at least 60, although in their juvenile forms they may reach as 

 low a value as 52. 



With regard to the inclination of the plane of the foramen magnum. Bolk (42) 

 proves conclusively in his paper that a change in the slope takes place during de- 

 velopment both in the human subject and in the anthropoids, but less well marked 

 in the former ; the young anthropoid in this, as in many other features, agrees more 

 closely with the human condition than the adult one. Man occupies a distinct 

 position amongst the primates in that the opening is turned towards the front and 

 not towards the back. 



In Bolk's method if the angle is equal to 90° the plane of the foramen magnum 

 is parallel to the base line and is considered to be horizontal ; if greater than 90°, the 

 foramen looks forwards to a degree which increases as the angle increases. Bolk 

 gives the size of the mean angle for a number of races, and we can compare the angle 

 of the Scottish series with these. 



In Papuans the angle is equal to 



In Negroes 

 In Javanese 

 In Zeelandians 

 In Frisians 



101-9° 



99'2° 



99*4° 



102-3° 



96-2° 



In the Scottish series the mean angle for the 98 was 94'80°, but showed a range 

 in value from 84° to 112°, so that the mean inclination of the foramen magnum was 

 not so much forward as in any of the races for which values are quoted by Bolk, 

 although in one case the basal angle was 112° and in a number of others it was over 

 100°. It is generally believed that in the European the plane of the foramen 

 magnum is directed forwards to a greater degree than in the Negro, but so far as my 

 figures are to be depended upon it would appear that in this Scottish series of skulls 

 the inclination of the opening is directed forwards on the average to a less-marked 

 degree than it is in such a primitive type as the Negro. There is a distinct gap 

 between the values shown by the angle in the human skull and that of the anthro- 

 poids, in which the angle varies from 70° to 75°, although in the infantile gorilla an 

 angle of 95° has been found. The smallest angle in the Scottish series was 84°, while 

 two showed an angle of 85°, one an angle of 86°, five were 87°, and four were 88°. 



There are certain lines measurable on the mesial sagittal section, and we can 

 compare the mean values of those given by Turner for the corresponding measure- 

 ments in his series in the form of a table (LIII). 



