274 THE KETINA, BY MAX SCHULTZE. 



by a somewhat greater degree of resistance, permitting themto 

 be isolated, whilst the intervening spongy tissue becomes broken 

 down or destroyed. Small tags or fragments of the spongy 

 tissue, or at least lateral processes, always remain attached here 

 and there to the radial supporting fibres, and give rise to the 

 peculiar and quite characteristic roughness of their surface. 

 But the plexus, which, like a sponge, consists not only of fibres, 

 but of membranous plates, forming shells and sheaths around 

 the nervous elements, varies in thickness in accordance with 

 that of the different layers of the retina, contains large spaces 

 for the reception of the ganglion cells, smaller ones for the 

 internal granules, and still finer ones for the nerve fibres of the 

 two granulated layers.* The radial fibres are often seen to 

 break up completely into spongy tissue, and thus it comes to 

 pass that many of them which maybe folJowed outwards from 

 the limitans interna through all the layers, ceasef in the external 

 granulated layer, and therefore do not reach the outer granule 

 layer. On the other hand, many radial fibres which may be 

 followed into it from the outer layers, disappear in the plexus 

 of the internal granulated layer.:}: Lastly, radial fibres may also 

 be met with, which reach neither of the membranse limitantes. 

 The radial supporting fibres are most constantly found in 

 the internal granule layer. The greater number of them here 

 also contain in their substance oval homogeneous nuclei, with 

 distinct nucleoli. In general it is impossible to discover any 



* In opposition to the different views that have been advanced in 

 regard to the structure of the young tissue of the granulated layers (see 

 Henle and Merkel in the Zeitschrift fur rat. Med., Band xxxiv., 1869, 

 p. 51, et seq.), I can only repeat what I have already stated in my Unter- 

 suchungen uber den Ban der Nasenschleimhaut, ("Researches on the 

 Structure of the Mucous Membrane of the Nose,") p. 29, Halle, 1862. I 

 willingly admit that our microscopes and methods of preparation are in- 

 sufficient for the investigation of the granulated substance of the cerebral 

 cortex, but the spongy substance of the retina in the granulated layers 

 is distinctly resolvable into a plexus of fibres, if due care be taken in its 

 preparation, and if its examination be undertaken with our best immer- 

 sion-lenses. 



t Max Schultze, Archiv fur Mikroskop. Anatomie, Taf. xiv., fig. 6, 8 b, 

 8 c, 10 6. 



J Ibidem, Taf. xi., fig. 13. 



