22 



Golding Bird and Schäfer, 



Thickness of retinal layers. 



rs mm. from fovea 

 mesial lateral 



At edge of fovea 

 mesial lateral 



At centre 

 of fovea 



Pigment-cell layer . 

 Rod and cone layer . 

 Fibrous layer . . . 

 Outer molecular layer 

 Inner nuclear layer . 

 Inner molecular layer 

 Ganglionic layer . . 

 Nerve fibre layer . . 



Total thickness 



0-015 

 0-045 

 0-130 

 0-005 

 0-050 

 0-025 

 0-025 

 0-025 



0-396 



0-015 

 0-040 

 0-105 

 0-005 

 0-050 

 0-030 

 0-035 

 0-015 



0-016 

 0-040 

 0145 

 0-005 

 0-075 

 0-025 

 0-070 

 0-020 



0-356 



0-320 



0-016 

 0-040 

 0-140 

 0-005 

 0-070 |-| 

 0-020 ) I 

 0-055 

 0-010 



0-295 



0-016*) 



0-090^) 

 0-064 



0-022 



absent 

 absent 



0-192 



Other measurements at fovea. 



Diameter of outer segments of cones at extreme centre . 0-0020 mm. 

 Diameter of inner segments of cones at extrem ì centre . 0-0021 „ 



Diameter of cone nuclei at extreme centre 0-0057 „ 



Diameter of nuclei of bipolars 0-0043 mm. 



Diameter of ganglion cells 0-0140 „ 



Diameter of "dislocated" nerve-cell close to centre. . . 0-0130 „ 



Extreme width of internal fovea 1*1 „ 



Extreme width of external fovea 0-8 „ 



Depth of internal fovea 0-130 „ 



Depth of external fovea (measured to prolongation of re- 

 tinal curve) 0-133 „ 



The figures on Plate I are photographs from a section passing 

 horizontally through the middle of the fovea. In all the figures, the 

 nasal side of the section is to the left and the inner surface looks 

 downwards. The limitans externa is very distinct but the limitans 



') The measurement of the pigment -layer in the centre is adopted from 

 H. Müller as the layer was detached just here in our specimens. 



') This is taken not from the specimens which are photographed, in which these 

 structures were ill preserved, but from another (osmium-bichromate) preparation in 

 which they were very well kept. But even here the pigment layer was detached 

 and with it the ends of the outer segments so that probably the cones should be 

 somewhat longer than this. 



