PROJECTION OF THE RETINA IN THE BRAIN 19 



The secondary degenerations after macula lesions were 

 very distinct. Two points struck us here. First, that the 

 degeneration after lesion in the macula is very large. The 

 macular fibres are widely spread throughout the corpus 

 geniculatum externum. They are chiefly found in those 

 parts of the gangKon where degenerated fibres were not 

 present after lesions of the upper and lower halves of the 

 peripheral retina, that is, in the centre. Secondly, that in 

 the oral part there is an overlap between the degenerated 

 spots after injury of the macula and outside of the macula. 

 The question now arises whether this is a real or only an 

 apparent overlap. This matter cannot be decided with ab- 

 solute certainty as we have here reached the limits of 

 Marchi's method, but we have the feeling that there is not 

 a real overlap. During our investigations in rabbits and 

 cats the probability of a sharp localization always forced 

 itself on us. This is also the case in monkeys and especially 

 also in macula-lesions. When Professor Zeeman extirpates 

 only the upper part of the macula, a large degeneration is 

 seen in the geniculate body, but it shows a clear tendency 

 to remain medially. But when he operates on the lower 

 half of the macula the degeneration always tends to go 

 laterally. Hence the upper part of the macula lies in the 

 immediate neighbourhood of the upper part of the periphery. 

 It is only in the more oral sections of the external geniculate 

 body that this sharp locaUzation is not found. We must 

 not forget, however, that a large part of the optic tract 

 passes through the oral part of the ganglion, and we believe 

 that many of these fibres only penetrate this portion of the 

 ganghon on their way to more central parts. 



Hence we arrive at the conception, given in figure 5. 

 In each geniculate body there is a small part for monocular 

 vision. This is represented at the ventral border of the 

 periphery. The greatest portion serves for binocular vision. 

 There is a sharp locaUzation, the upper half of the retina 

 lying medial, the lower half lateral. The macula has a 



