not dependent merely on the direction of the Foramen magnum 
because the direction of the base-line, i. e. one of the legs of the 
angle, depends on several factors, e.g. the angles of the basis cranu, 
the length of the skull, the length of the clivus, the position of the 
nasion, etc. To avoid this difficulty Broca determined the slope ot 
the For. magn. by an angle made by the plane of this opening with 
a plane which is entirely independent of the cranial base, viz. that 
which connects the axes of the two orbitae. He constructed his 
“angle orbito-occipital” 1 ). Broca here was proceeding from the postu¬ 
late that the orbital-plane, in Primates at least, is the natural hori¬ 
zontal plane of the skull, as, in the case of normal sight, these 
animals look straight before them and the orbitae in this circum¬ 
stance therefore will have the same direction. The correctness of 
this opinion will be discussed in a following paper. 
Rauber 2 * ) in a recently published treatise, returns to the old, 
disused method, takes as base-line again the nasion-basion, and even 
says that: “eine Beziehung der Neigung des Foramen occipitale auf 
eine andere Linie als auf die Basallinie fiihrt sehr leicht zu Unver- 
standlichkeiten und entbehrt zugleich der morphologischen Bedeutung”. 
Schwalbe, also, lately expressed as his opinion regardmg the value 
of Aeby’s base-line as follows: “So rationell auch die von Aeby 
gezogene Grundlinie ist, ist sie doch nicht geeignet liber die Aus- 
bildung der verschiedenen Teile des Schadelraumes Auskunft zu geben. ) 
There is a certain contradictoriness in this criticism. A rational 
base-line of a eraniometrical system must be able to serve as basis 
for at least a primary division of the skull. I have already briefly 
stated my objections to base-lines which are drawn through the 
skull-base, and will come back to this subject in a following paper. 
Such a line may have a certain value as boundary line between the 
cerebral- and facial-skull, but as basis of a eraniometrical system 
it is absolutely useless. __ 
Huber 4 ) finally has determined the slope of the For. magn. in 
Hylobates with regard to the so-called German horizontal, a method 
which when the skulls to be examined cannot be halved medially 
is preferable to those of other investigators. The probable error will 
here be less than by the use of the basal line and certainly likewise 
less than bv employing the horizontal auxiliary line made use of by 
>) P. Broca. Sur l’angle orbito-occipital. Revue d Anthropologie 1897. 
V) A. Rauber. Der Scbadel von Kegel, lnt. Monatseh. f. Anal, und !%».««*• 
*> G. Schwalbe. Kritik zu Kohlbruooe’s : Morpkologmche Abstammung dee Men- 
schen. Globus 11 Juni 1908. , „ , , iqao 
4) L. Huber. Vergleichung des Hylobates und Menschenscbadels. Munchen 1902. 
