( 205 ) 
In order to point out the failing cortex-part it is necessary to 
have a punctum fixum, which has a constant position in the topo¬ 
graphic constellation. 
It seems to be allowable to regard as such a point the frontal 
border of the foramen Monroi. This choice is certainly justified by 
embryologic considerations (constant position of the lamina terminals ; l ). 
The projection of this point on the lateral wall of the hemisphere 
appears to lie nearly in the fiss. praecentrails, about 2 centimetres 
dorsally to the ventral border of the operc. frontale. 
In our case the latter distance is much smaller, the point of pro¬ 
jection falls only one millimeter in front of the junction of the horizontal 
and vertical sulci operculares. In regard to the ventral-orbital border 
of the operculum its position is not the same on the left and right 
hemisphere. On the left the normal condition is found, but on the 
right the ventral-orbital border of the operculum appears to be 
shifted in a frontal direction. Correcting in this way tho insufficiency 
in the opercularisation above mentioned we see that only the ventral 
insula-part remains uncovered. If my supposition that this defect is 
not due to the insufficient expansion of the frontal cortex, is correct, 
only a subnormal development of the temporal lobe in a frontal 
direction can be considered to be the cause. Controlling this presumption 
by the- topical relation of the temporal pole to the above mentioned 
projection-point we find the horizontal distance to be about 1 cm. 
less than in normal brains. — Bolk l.c. calls attention to the phylo¬ 
genetic increase forwards of the temporal lobe; the fissura Rolando in 
its ventral continuation is used by him as a topic criterium. In our 
case I thought it better not to use this criterium. (N.B. the asymmetry 
of both fiss. centrales!); in another way however, a similar result 
was obtained. 
If the extension of the temporal lobe is corrected in the drawings, 
not only an operculisation of the insula is obtained but also a more 
normal direction of the fissura Sylvii instead of the almost vertical 
furrow, of which only the posterior part represents the fissura Sylvii, 
whereas its frontal part is only a fold between the island and the 
temporal cortex. 
The particular aspect of the surface of the brain is the expression 
of the internal stature of the cortex . The latter again is determined 
by the general laws of development in regard to eventual abnor- 
!) The limits of the corp. callosum — although used in the division of normal 
surfaces (v. Monakow) - cannot here be made use of, because, proportionally to 
the surface of the brain (ffie parts of which should be topographically determined) 
it varies in size. 
