240 THE RETINA, BY MAX SCHULTZE. 



the appearance of being finely striated longitudinally, and 

 therefore give some indication of being composed of fine fibrils, 

 which we regard as characteristic of all the thicker axis- 

 cylinders (fig. 350). 



On reaching the external granulated layer, the cone fibres 

 present a peculiar modification ; each forming at the outer sur- 

 face of this layer a conical triangular enlargement (fig. 348, 6), 

 beyond which it is impossible to follow the fibre continuously.* 

 These are so firmly imbedded in the substance of the exter- 

 nal granulated layer as to give the impression that they are 

 continuous with it. The cone-fibre spheroids, when isolated, have 

 for the most part fragments of the granulated substance still 

 adherent to them, supporting the view of their continuity. It 

 is true that the conical enlargements in question here break up 

 into fine fibrils, but these are different from those of the plexus. 

 In successfully made preparations of the retina of Man, mace- 

 rated in iodized serum, I have seen the conical enlargement break 

 up into a brush of numerous and extremely fine fibrils, which 

 were not joined together in a plexiform manner. f If we com- 

 pare with this appearance that of the network of the external 

 granulated layer, similarly hardened and isolated, the difference 

 between the two kinds of fibres becomes exceedingly evident. 

 This is further evidenced, on the one hand, by the ease with 

 which the continuity of the plexus with the radial supporting 

 fibres can be demonstrated ; and on the other, by the manifold 

 differences in appearance between the latter and the cone fibres, 

 especially in the disposition to form varicosities, exhibited by 

 the latter and* the nerve fibres on their side, but which does 

 not occur in the radial supporting fibres, whilst these, on the 

 other hand, are characterized by their peculiarly rough surface. 

 With these facts, the relation of the cone-fibre enlargement to 

 the external granulated layer cannot, as is believed to be the 



* H. Miiller, Zeits. fur wissenschaft. Zoologie, Band viii., Taf. i., figs. 1 

 and 3 ; Henle, Eingeweidelehre, p. 650 ; M. Schultze, Archiv fur Mikros- 

 kop. Anatomie, Band ii., Taf. xxxi. 



t Hasse (Zeitschrift fiir rat. Med., Band xxix., p. 252), believed that 

 in all instances three of such fibrils emanated from each conical en- 

 largement, whilst Merkel, loc. cit., p. 7, considers that (at the macula lutea 

 at least) a bifurcate division normally occurs. 



