PROJECTION OF THE RETINA IN THE BRAIN 21 



pretty large projection between them, but it is a localised 

 one. The upper quadrant of the macula borders on the up- 

 per part of the peripheral retina and the lower part of the 

 macula on the lower periphery. Further we believe that 

 the horizontal meridian of the retina remains vertical, but 

 somewhat oblique, in the corpus geniculatum externum. 



You may now ask me, what is your opinion about the 

 more central localization in the brain? I am at present 

 engaged in my laboratory with this side of the problem and 

 hence cannot give sufficient data. I am convinced, how- 

 ever, that the various opinions, generally held at this 

 moment, cannot be correct. Because the results of our 

 investigations enable us to conclude, that in monkeys — 

 and also in men- — two parts have to be distinguished in the 

 optic cortical centres, one for monocular and one for bin- 

 ocular vision. As regards the projection of the retina for 

 binocular vision the idea of an exact locahzation must give 

 the lead. But we are sure that the macula cannot be pro- 

 jected on a small isle of the calcarine. This projection must 

 be a locaHsed one, but it must be a large one. We have seen 

 that the macular fibres are very widely distributed in the 

 external geniculate body, but that a localization exists 

 cannot be denied. On more careful examination we find 

 a difference between macula and non-macula lesions. In 

 the former the distance between the degenerated fibres is 

 greater than in the latter. Hence they may touch more cells 

 there than the fibres of the periphery. In many respects 

 our results resemble those of Ronne in man. He studied the 

 atrophy of the cells of the external geniculate body in cases 

 where the macular bundle was degenerated as a result of 

 chronic intoxication; he found that in man the macula is 

 projected on the dorsal part of the ganglion. Ronne con- 

 cludes that his findings prove the connectness of Henschen^s 

 hypothesis. His diagrams, however, show that the distribu- 

 tion of fibres in the external geniculate body is wide. 



As mentioned already above, views on the representation 



