16 Golding Bird and Schäfer, 



and indeed the method of preparation employed would, we believe, not 

 have tended to produce this effect. The outer segments measure 

 slightly less than tlie inner. We are therefore inclined to think that 

 a measurement of 0-002 mm. represents as nearly as possible the 

 diameter of the outer segments at the very centre 



4. As to the position of the cone-gramdes in the fibrous layer 

 (outer nuclear layer) of the fovea. 



The cone granules, which are packed close against the limitans 

 externa in other parts of the macula lutea, are at the very centre of 

 the fovea placed in the inner part of the fibrous layer, almost as far 

 as possible fi'om the external limiting membrane. They begin to leave 

 their position close to that membrane at the edge of the external fovea 

 (Fig. 2) and at the same time acquire a less closely packed arrangement; 

 and they gradually increase their distance from the membrane as we 

 approach the centre. The cone-granules are more numerous opposite 

 the margin of the fovea than anywhere else in the retina, being at 

 least five or six deep here; and in consequence of their looser arrange- 

 ment they occupy even relatively to their number a greater part of the 

 thickness of the fibrous layer than in the adjacent macula. As they 

 attain in approaching the centre a deeper position in the layer they 

 very gradually diminish in number and towards the centre of the 

 fovea they are only two or three deep. 



It will have been noticed in the introductory account which we 

 have given, that more than one previous observer has described or 

 pictorially represented the cone-nuclei as being less closely ajiplied to 

 the limitans externa within the fovea than elsewhere. For the most 

 part, however, their position as given in Max Schultze's diagram has 

 been accepted. Schwalbe is the only one who has laid stress upon 

 the fact that tliey are no longer applied to the membrana limitans 

 exteina in this region; but even he does not nearly approach the truth 

 as regai'ds the position of the cone-nuclei at the centre of tlie fovea, 

 for in the first place he represents them there as only one deep and 

 secondly as still lying nearer to the limitans externa than to the 

 molecular layer. Our specimens through the fovea] centre show them 

 here, to be jiliiiost resting upon the outer molecular layer. 



