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Now we know that the lobi parietalis and occipitalis are sepa- 
rated, on the surface of the hemisphere by the s. par. occ. lat. 
(m + m’) and on the medial surface by tbe s. par. oce. med. (w), 
while the lateral border is formed by the s. occip. inf. (6). 
3efore the formation of the apefissure there are between these 
sulei bridging convolutions which pass from the one lobus to the 
other. 
The first communication comes from the arcus parieto-occipitalis 
along the medial end of the m’ and continues in this way on the 
occipital surface (on fig. 2 this communication first goes between 
14e and w, and later medially from m’. On fig. 3 it is indicated 
by the arrow sub I. One sees it deviating occipitalwards to the 
lateral and medial surface). 
The second communication comes from the gyrus angularis (fig. 
3 sub 2) and from the gyrus temporalis II (fig. 3 sub 3), to pass 
as a single convolution between the suleus oce. inf. and the lateral 
part of the sule. par. oee. lat. (m), towards the lobus occipitalis. 
The third communication is found on the medial surface, beneath 
the suleus par. oee. medialis. It is the gyrus cuneus of Ecker, which 
iel 
vLlauAdAe. 
326 
vlakte = surface 
Fig. 3. 
here connects the praecuneus with the cuneus. The arrow sub 4 
indicates on fig. 3 the direction of the communication. 
In semnopitheci one therefore finds three bridging convolutions 
lying on the surface, between the parietal and temporal part on the 
one side and the lobus occipitalis on the other side. These three 
communications are the plis de passage. 
