2 g John Grattan : 



against the base of the skull. The skull can then be rotated along 

 with the stage to which it is fixed, round an axis passing through 

 the external auditory openings, or it can be rotated along with its 

 stage round an axis perpendicular to the first. In each case the 

 exact amount of rotation is indicated by a dial. The instrument 

 has a brass carriage, a brass slide and a curved tracer, all suitably 

 adjusted, so that the distance of any part of the median line of the 

 skull from the point where the axis passing from the centre of one 

 ear-opening to the other crosses the median plane, can be read on 

 a graduated scale marked in inches and tenths of inches. Grattan 

 selected as his starting-point, or zero, the distance from this point 

 on the auditory axis to the nasion, or depression just above the 

 root of the nose. After this is ascertained the brass slide is with- 

 drawn, the skull rotated io°, the brass slide carrying the pointer 

 again pushed towards the skull and the distance measured in the 

 same way as from the nasion. This process of skull rotatiou 

 through io° and of measurement is repeated along the entire 

 extent of the arc. From such a series of measurements a profile 

 drawing of the skull can be made showing the position of the 

 external auditory meatus and the coutour of the vault at intervals 

 which, in an ordinary skull, are less than an inch apart. If necessary, 

 the skull can be measured at shorter intervals by rotating the skull 

 between each measurement a smaller number of degrees. By 

 other adjustments the same instrument can be used to make a 

 tracing on paper of the external contour of this arc. After the 

 vault has been measured the rotation of the skull can be continued 

 so as to determine the amount of projection of the nose, jaws, and 

 teeth below and in front of the cranium. Grattan measured a 

 number of skulls in this way and compared them with one another 

 in a series of tables showing the proportion of the radial diameters 

 at io° interval from zero to 180 with the length of the skull 

 estimated at ioo°. 



It is difficult to imagine a more ingenious and accurate method 

 of measuring this part of the skull. 



The length-breadth index expressed by comparing the greatest 

 length of the cranium with its greatest breadth is open to the 



