STUDIES IN THE RETINA. 63 



This demonstration is afforded us by the fact that in the 

 baboon's eyes the pigmented matter retains its colour right 

 through the retina, being only slightly less bright and 

 refractive near the internal limiting membrane, Avhere it is 

 present in enormous quantities. In the youngest baboon's 

 retina the congealed vitreous humour was left in situ in the 

 base of the retinal cup, and appears in the sections. Its 

 layers nearest the retina are coloured like the 

 pigmented matter on the retinal side of the internal 

 limiting membrane.^ 



Returning to our review of the passage of the matter 

 absorbed by the rods through the retina, we have seen that 

 ii, instead of the matter having to travel along zigzag paths 

 on the strands of the cytoplasmic reticulum, it found a sufficient 

 number of radial strands running in continuous courses right 

 through, the passage would be much simplified. All the accu- 

 mulations of matter which we have described in the eyes of fish 

 might be avoided. The most perfect radial strands which I 

 have ever seen running through the inner reticular layer occur 

 in sections of a human retina" which, from the scarcity of the 

 nuclei in both the nerve-fibre layer and the middle nuclear 

 layer, and from the condition of the inner reticular layer, I 

 take to be that of an old individual (see fig. 32, a). It is hard 

 to believe that such " Miiller's fibres " as these were not per- 

 manent structural elements ; if they were they had become so 

 only during life, and to meet special functional requirements, 

 for in the normal healthy retina of a man of forty-eight, 

 referred to above, hardly a single straight radial strand can be 

 found through the whole inner reticular layer. Faint zigzag 

 streams alone occur here and there (fig. 32, h), but are not 

 numerous. That there should be no pronounced " Miiller's 



' As this abborbed niallur sUoains lluougli all parts of tlie letiiiu (except 

 tlie Ijliiid spot,), and during a lifetime of fuuctioninj,', it is clearly a factor 

 wliicli no student of the vitreous humour can afford to ignore. It suggests, 

 for instance, a new and very simple explanation of Stilling's canal. 



^ Purchased many years ago from Messrs. Watson, of Holborn, in a series 

 of slides to illustrate the structure of the eye. 



