23 
should rest, generally about two millimetres above the level 
of the transverse axes of the eyes. 
4. Breadth of Nose. —Measured across the widest part 
without compressing the nostrils between the points of the 
instrument. 
These two measurements give the nasal index, the 
* i , . Breadth X 100 
formula of which is - t -ir-= nasal index. 
Length 
The next four measurements show the distance their 
several levels project vertically below the plane of the top 
of the head. For directions as to how the instrument is 
to be used in determining them see Instruments, p. 9. The 
position in which the head is held by the subject while 
these measurements, and also those of height, are being 
made is most important and requires the careful attention 
of the observer. The subject must sit with the body upright 
and the head straight, the line of vision directed horizontally 
forwards to a point at a little distance off, the same height 
as the eyes. Having adjusted the head in the proper position, 
the instrument is placed with one limb resting on the 
vertex while the body of the instrument is held vertically 
in front of the face ; to secure this being done a small 
plumb-line should be temporarily fixed to the base of the 
curved part of its upper arm or on the end of the carrier, 
Plate lie. After each measurement is taken the observer- 
should see that the subject is in the correct attitude before 
taking the next. 
5. Vertex to Root of Nose .—The point on the root of the 
nose to which this measurement is taken is the same as 
that in measuring the length of the nose, Plate lie. 
6. Vertex to Mouth. —The lower point is the line of the lips 
when closed, Plate lid. 
7. Vertex to Chin. —The point on the chin is that corres¬ 
ponding to the under surface of the lower jaw, as shown in 
Plate II. 
8. Vertex to Tragus, of Ear , or supra-auricular projection, 
is measured by rotating the instrument to the side of the 
head, the horizontal arm still resting on the vertex. The 
