( 202 ) 
Anatomy. — “Surface and structure of the cortex of a microct- 
phalic idiot ” By Dr. C. T. van Valkenburg. (Communicated 
by Prof. L. Bolk). 
The woman, whose brain was examined, represented a case of 
not very grave idiocy, without important motor, sensible and sensory 
troubles. Causa mortis: tuberculosis pulmonum, at 38 years 1 ).- •• 
Weight of the whole brain 390 grams. 
The surface of the hemispheres shows a striking resemblance lo 
the condition presented by the human foetus specially in the frontal 
part; in tlie parieto-occipital region the development seems more 
anthropoid. 
From a confrontation of several foetal brains with anthropoid 
and normal human brains the following statements result. 
The few furrows, (almost exclusively primary ones are present) 
show for the greater part the simple condition as presented in foetns; 
they limit broad circumvolutions which give to the brain a macrogyric 
character, specially in the frontal and temporal lobi. 
The parietal-occipital region shows the greatest lack of development, 
as is proved by the greater abnormalities in gyri and sulci. 1 
Specially in the parieto-occipital “plis de passage” the abnormalities 
show a tendency in the direction of the anthropoid type. It is easy 
to see the character of the simian split in the system of the neigh¬ 
bouring furrows. 
A simian split is present, when the parieto-occipital plis de passage 
are entirely or partly operculated by the occipital cortex. Sensu 
strictiori one cannot speak of a fissure in such a case, (as neither^ 
can be done with the sulci operculares insulae). Already this fact 
is sufficient to prove, that in principle it is wrong to accept in the 
human brain a simian split in those cases where the tiss. par. oce. 
is continuous with a transversal fissure on the par. occ. convexi J 
as is generally done. (A similar condition is found in our case 
the right side of the brain). ^ 
A continuation of the posterior wall of fissure a in a ^ 
direction over the anterior furrow Of the delta-shaped complex w0U 
give rise to the formation of an operculum covering the entra 
to the simian split. ., ^ 
In the condition as it is now the fissure a can be only consi 
as the caudal border of a virtual simian split. — 
9 From the cases described in detail, only one patient reached a j^ 
from Hilty, (v. Monakow’s laboratory); the grea roa . 
(49 years): ca 
young children, 
