32 LECTUEE II. 



surement, that it cannot show such differences as are found in 

 the development of the forehead and the vertex. 



If we return from this digression to the investigation of the 

 normal base line, upon which measurement must depend, we 

 find the same difficulties in determining a universal horizontal 

 plane, as in determining the normal vertical one. In perfect 

 repose the head is balanced upon the topmost vertebra, the 

 so-called atlas, but as is easily seen, this equihbrium is dis- 

 turbed both in the living subject and in the dead skull, in the 

 most various ways. If, however, the above position is assumed 

 as the normal, then selecting as the starting-point the aperture 

 of the ear, the horizontal line passes nearly through the centre 

 of the nasal aperture, a little above the point of the nose, in 

 the living man, A horizontal line must, therefore, be assumed 

 (its importance will be seen in the sequel), which can be de- 

 termined by its terminal points, though it causes the head to 

 deviate slightly from the natural position. 



The half-dozen anthropologists who met at Gottingen, in the 

 autumn of 1861, had a hvely discussion with regard to the 

 Hne, or rather the plane, which ought to be assumed as the 

 horizontal. One proposed the zygomatic arch ; another, a plane 

 passino- across the occipital foramen ; a third, a hne from the 

 auditory aperture to the base of the nasal aperture. The zygo- 

 matic arch is never quite straight; the direction of the hori- 

 zontal line passing through it must frequently be taken more ac- 

 cording to the feeling than actual measurement. Even if we 

 could succeed in laying a plane exactly across the occtpital fora- 

 men — a task of considerable difficulty on account of its form — 

 it cannot be determined in the living head, and as this plane 

 is so short, every error would be magnified by the necessary 

 prolongation of it. The only horizontal plane which can be 

 termed rational is that between the two aural apertures and 

 the bottom of the nasal apertures, and which may be deter- 

 mined both on the living head and on the skull. The hori- 

 zontal line drawn in this way, between two fixed points, 

 easily determinable both on the living head and dead skull, has 

 moreover the advantage of representing one of the Hnes of Cam- 

 per^s facial angle, which has been long in use, and although defec- 



