Wyman.] 



44G 



[April 15, 



from the glabella to the occiput, having been previously measured 

 with the callipers, is made horizontal by bringing the two ends of it 

 to correspond Avith the points of the indices on the graduated uprights, 

 and on which the indices are adjusted to the same elevation. Two 

 moveable plumb lines, susjDended from a wire stretched across the 

 upper part of the frame, are then so adjusted that one dropping 

 through the foramen magnum touches its anterior border, while the 

 other touches the most prominent part of the occiput. The position 

 of the foramen is indicated by the ratio of the distance comprised 

 between the two plumb lines, to the long diameter of the cranium 

 projoer. The number expressing this ratio may be called the index of 

 the foramen magnum^ thus conforming to the method of expressing the 

 ratio of the breadth, or the height to the length. When it is said that 

 the index of the foramen magnum is 45.4, it is understood that the 

 distance of the anterior edge of the foramen from the most projecting 

 part of the occiput, is 45.4 parts of the long diameter, this last being 

 considered 100, and both being pi-ojected on to the same plane. 



To avoid error, it is important that the long diameter of the head 

 should be made as nearly horizontal as possible, for the foramen mag- 

 num being on a higher plane, moves through an arc of a circle, 

 which, as the long diameter is tilted backwards or forwards, changes 

 the position of the point where the vertical cuts the horizontal line. 



The preceding table, in which the number of the skulls of each 

 race examined is given at the top of the respective columns, shows 

 that there is an actual difference in the position of the foramen mag- 

 num in the races compared, and of such an amount as to make it 

 desirable to test the result with much larger collections, in order to 

 determine more precisely the value of the position of this opening as 

 a race character. 



