( 935 ) 
All independent investigators agree on this point, that the fovea 
centralis must be represented in a special manner on the cortex. 
They are torced to acknowledge this by the fact, that the hemianopsy 
determined by occipital foci is always incomplete, i.e. there is still 
a remnant of the field of vision that has not become blind, and to 
this remnant belongs the fovea. 
Therefore this latter must be represented in a particular way in 
the cortex. 
Jut there is a great divergence of opinions about the manner in 
which this particular representation is effected. 
Some investigators claim for the fovea a separate cortical area 
(situated eg. at the bottom of the fissura calcarina, HENscuen, SACHS, 
WILBRANDT). 
Others believe the fovea centralis to be localized in a diffuse 
manner in a very extensive cortical area (to which should belong 
not only the environs of the fissura calearina, but also at least the 
occipital gyri, von Monakow). 
This divergence of opinions may easily be understood. After it has 
been proved (Forster, among others) that the patient with bilateral 
hemianopsia still possesses a central remnant of the field of vision, 
there remain only two possibilities. 
Either in these cases, there remains intact on both sides a cortical 
area of the fovea, — or the diffuse dispersing of the fibres con- 
ducting the fovea-impulses towards an extensive optical cortical field, 
allows the possibility that even after a relative extensive destruction 
of cortex and fibres, a certain number of these fibres may have 
been left intact, and consequently central vision unimpaired. 
As however, until now, there were known no well ascertained cases 
of central hemianoptie scotoma, dependent on accurately demonstrated 
occipital foci, the partisans of a diffuse localization of the fibres of 
the fovea have a decided advantage over those, who defend the 
especial cortex-area of the fovea. 
The second, new proposition of Nirssr, interferes in a peculiar 
way in this dispute. 
The field of the fovea of Nirssi is no longer the fovea-field in the 
fiss. calcarina, as it has been conceived by HueNscHeN among others. 
The fovea-fascicle of Nissi irradiates into the dorso-lateral mass of 
the strata sagittalia, towards the basal occipital gyri and even in the 
cuneus, not into the calearina-field but around it. 
This fascicle being interrupted (e.g. by a softering focus in the 
g. angularis or by the destruction of its cortical field), the ensuing 
symptom will be, no longer a central hemianoptic scotoma, but, 
61 
Proceedings Royal Acad. Amsterdam. Vol. XIII 
