25G THE RETINA, BY MAX SCHULTZE. 



no distinction has hitherto at least been made out between the 

 superficial and the deep fibres. The internal fibrils (which I 

 have already imperfectly depicted in the Archiv fur Mikroakop- 

 Anatomic, Band ii., Taf. x., fig. 8) do not extend quite down to 

 the limitans externa, but cease abruptly at a certain distance 

 from it. At any rate, they here become invisible, and if they 

 extend any further towards the cone fibre, change their nature. 

 Cones are found containing small spheroidal particles like fat 

 drops at the point where the internal fibrils appear to cease, 

 whilst there are others that have snapped across at this point. 

 In the fresh condition the fibrillated portion of the cones 

 appears as a brilliant strongly refractile body. By careful 

 maceration the fibrils may even be isolated. They cease at the 

 point where the outer segment commences. The connection 

 of the outer with the internal segment appears also to be 

 effected by a sheath investing the fibrillar substance. 



I have been able to recognize a very similar structure, com- 

 posed of short stiff fibrils, in the interior of the inner segments 

 of the rods in Man (fig. 356, A, s s). The appearances presented 

 are precisely similar to those of the cones, and corroborate the 

 view, otherwise well established, that independently of the 

 different thickness of the nerve fibres belonging to them, no 

 essential difference exists between the rods and cones beyond 

 that of form and size, and that thus these two forms of perci- 

 pient elements are only modifications of a type common to 

 both. 



With the rods and cones we have arrived at the end of the 

 expansion of the optic fibres in the retina, and if we now take 

 a general view of the connection of the nervous elements of 

 the retina of Man, as we are justified by our present knowledge 

 in stating it, we find, in the first place, (see the adjoining 

 schematic representation,) that the non-medullated nerve fibres 

 of the optic layer are directly continuous with ganglion cells. 

 At the macula lutea, where this connection is particularly obvi- 

 ous, all the ganglion cells are bipolar. The peripheric process 

 is the thicker of the two, and enters the internal granulated 

 layer, where it divides. In other parts of the retina the gan- 

 glion cells appear to be for the most part multipolar, in which 

 case there is probably one central process given off into the 



