PROJECTION OF THE RETINA IN THE BRAIN 5 



to how the optic fibres are spread throughout the central 

 nervous system. The chief representatives in this field are 

 two celebrated workers, S. E. Henschen and C. von 

 Monakow. 



Henschen holds the localizations theory. In his opinion 

 every spot of the retina has a sharp localization in the 

 geniculate body, in the central optic radiation, as well as in 

 the cortex. Also in his review of 1924 he holds a mathe- 

 matical projection of the retina in the calcarine cortex. The 

 upper half of the retina always lies dorsal in the optic path- 

 ways, the lower half ventral. The significance of this con- 

 ception for clinical purposes is evident. When a tumour 

 destroys the whole cortical centre on the right side, we get a 

 left-side hemianopsia. When a tumour only destroys the 

 dorsal half, we get the symptom of hemianopsia inferior. 

 Inferior because the light stimuli, which are caught by the 

 dorsal half of the retina, come from the inferior half of the 

 field of vision. Pathological processes in the ventral part 

 of the calcarine cortex must cause hemianopsia in the dorsal 

 half of the field of vision. 



In Henschen's opinion the macula forms no exception. 

 It must be locahzed like an isle in the different pathways and 

 also in the cortex. Views on the representation of the 

 macula in the calcarine cortex have varied in his papers. 

 Lately Henschen accepts the opinion, that the macula must 

 be projected near the occipital pole. 



von Monakow and his school do not believe, that the 

 different parts of the retina can be definitely localized in the 

 brain. The idea of a sharp localization does not appeal to 

 them. Above all von Monakow denies that the macula 

 has a circumscribed localization in the brain. In his opinion 

 an isolated representation of the macula in the central parts 

 of the brain is anatomically impossible. The high physio- 

 logical significance of the macula led von Monakow to put 

 forward the theory that the impulses from this part of the 

 retina are spread over the whole external geniculate body, 



