. NERVOUS CONSTITUENTS OF THE RETINA. '1'1\) 



from the eyes of an Elephant, that were not removed from 

 the body until seven days after death * 



Ganglion cells, with their processes, may be observed in the 

 perfectly fresh retina, if portions taken from the neighbourhood 

 of the ora serrata, and from the surface of which the vitreous 

 has been removed, are examined in serum, with this sur- 

 face upwards. Lying among the decussating nerve fibres, 

 and immediately beneath the membrana limitans interna, in 

 the same plane with the capillary bloodvessels, numerous gan- 

 glion cells may be then seen, which, by cautious manipulation, 

 the production of a cloudy appearance by coagulation being 

 avoided, and the pressure of the covering glass being gradually 

 increased, become more and more distinct, and well adapted 

 for observation, even with the highest powers. Such, so to say, 

 living ganglion cells (fig. 346, A) present an extraordinary de- 

 gree of transparency, since they contain only very small gra- 

 nules in their cell substance, and are composed essentially of 

 an almost hyaline mass, in which the perfectly transparent nu- 

 cleus, with its lustrous and often finely dentated nucleoli, lies 

 imbedded. Dead ganglion cells which in such preparations may 

 be found at the margin of the section, or where the retina has 

 been otherwise injured, present a totally different aspect, be- 

 coming, by coagulation, coarsely granular and perfectly opaque. 

 More minute examination of the former with higher powers, 

 shows that the fine granules of the cell substance lie to some 

 extent in rows, and are grouped in parallel striae, whilst the 

 non-granular cell substance appears also differentiated into 

 bands. This character is precisely similar to that which I first 

 described as occurring in the ganglion cells of the brain and 

 spinal cord.f The cell substance is hence probably fibrillar, and 

 contains, in addition, an interfibrillar granular substance ; but 

 the transparency of the cells of the retina during life is so great, 

 and the fibrils are so fine, that the image they present is less 

 distinct than that, for instance, of the cells of the spinal cord. 

 In the next place, the fibrils around the nucleus possess an 

 approximatively concentric arrangement, whilst at the peri- 



* Corti, Zeitschrift fur wiss. Zooloyie, Band v., p. 90, Taf. v., 1854. 

 t In this Manual, Vol. i., p. 171 et seq. 



