60 H. M. BERNAED. 



meshes of the now altered reticulum. Tliis fact is au absolute 

 demonstration that these" Miiller's fibres'^ are not independent 

 preformed structures, but merely cytoplasmic threads of the 

 retinal reticulum thickened with matter. When they run 

 quite straight without any zigzag we must regard it as due 

 to a gradually acquired radial rearrangement of the threads 

 of the reticulum (cf. fig. 32, a and h). 



Then, again, apparently at any point in the inner reticular 

 layer, these strands may end suddenly, and the staining 

 matter which was travelling along them may disperse 

 to right and left (fig. 28, c). Many of the different aspects 

 of the inner reticular layer are due to the presence of 

 this refractive matter accumulated in different ways along 

 its strands. One phenomenon is particularly suggestive ; I 

 refer to the darker zones which are frequently seen in it 

 running for longer or shorter tracts round the retina. ' I 

 have seen them frequently (see figs. 20, a, 22, /;, c, 24, a). 

 Borysiekiewitz has also called attention to them. These 

 dark zones are, as it Avere, waves of absorbed matter, records 

 of former periods of functional activity, passing through the 

 retina. This is not evident microscopically when the reti- 

 culum is a close " Punktsubstanz," and the matter finely and 

 evenly dispersed, but becomes quite obvious when the reti- 

 culum is coarse and open, for then the individual strands of 

 the atfected part can be seen specially thickened (see fig'. 24, a). 



All these facts become so obvious to any one who will take 

 the trouble to study the retina comparatively that I feel it 

 almost unnecessary to discuss the details any further. One 

 or two points, however, remain to be noted. Just as the 

 streams end almost anywhere in the inner reticular layer, the 

 matter dispersing along the tangential strands, so fresh ones 

 may begin anywhere withiii the same layer. And this brings 

 us to the next layer, the nerve-fibre layer, or, as it is more com- 

 monly but less accurately called, the "ganglionic cell layer." 



The appearance of the strands which run radially from the 

 inner reticular layer to the mombrana limitans interna is well 

 known ; they are the typical inner ends of the^Miilier's fibres." 



