THE RETINA, BY MAX SCHULTZE. 



The concordant statements of Michaelis, H. Miiller, Henle, 

 Kolliker, and others, show that at the yellow spot an inter- 

 ruption to the regular radiating course of the nerve fibres in 

 the retina occurs, a continuous fibre layer being here defective, 

 and the fibres losing themselves in the thick ganglion-cell 

 layer, in order to enter into which freely, they form a series 

 of arches in the vicinity of the yellow spot. Liebreich* has 

 recently called attention to another peculiarity, namely, that 

 many more nerve fibres proceed directly upwards and down- 

 wards from the point of entrance of the optic nerve, than 

 outwards, though far larger tracks of the retina require to be 

 innervated in the latter direction. The fibres accompanying 

 the larger vessels, and running outwards, form arches around 

 the macula lutea where they terminate. 



On microscopic examination of an uninjured retina from the 

 inner surface, the nerve fibres may frequently be seen to be 

 grouped into fasciculi, between which are elongated fusiform 

 spaces.-)- These are occupied by fasciculi of the radiating sup- 

 porting fibres of the retina, which terminate in the membrana 

 limitans interna. Where, as at the ora serrata, the nerve fibres 

 are sparingly present ; or as at the macula lutea, are altogether 

 absent as a continuous layer, the ganglion cells come to be in 

 immediate contact with the membrana limitans interna. 



In exceptional cases in the human subject the medullary sheath of 

 certain portions of the optic nerve is retained beyond the limits of the 

 optic disk, and extends for some distance into the retina. This con- 

 sequently is rendered opaque, and when examined by direct light 

 appears white, as is well shown in the excellent ophthalmoscopic illus- 

 trations given by Liebreich in his Atlas of Ophthalmoscopy, Taf. xii., 

 figs. 1 and 2. Virchow:}: first established this fact in a man aged 

 forty-six, in whose eyes, after death, he found medullated fibres around 

 both disks, in one eye presenting the appearance of four diverging 

 radii ; in the other a hazy white annulus ; and since that date a series 

 of similar cases have been observed and examined both anatomically 



* Zehender, Klinische Monatsblcitter fur Augenheilkunde. Jahrgang, vii., 

 p. 457. 



t See H. Miiller and Kolliker, Retina-tafel in Eckers' "Icones," etc., 

 fig. 14. 



I Virchow's Archiv, Band x., p. 190. 



