80 W. J. DAKIN. 



existing- between the distal cells and the distal branch of the 

 optic nerve, so that these are also included as sense-cells, but 

 his views of the interstitial cells remain unaltered. He had 

 apparently neither seen nor heard of Hyde's paper, whicVi has 

 remained, therefore, uncriticised. Such is the mass of con- 

 flicting evidence at present existing. There is no doubt that 

 the relation of the distal nerve to the outer distal cells and 

 interstitial cells is the most difficult histological problem of 

 the retina. It is extremely difficult to trace the endings of 

 the nerve-fibres in sections, and impossible to make out the 

 shape of the interstitial cells. I have been able to make out, 

 however, the shape of the latter from macerations, and to 

 trace the extent of their branches, which can be confirmed by 

 sections. A schematic figure has been built up from macera- 

 tions and sections which shows the relation of the cells to one 

 another (PI. 7, fig. 13). 



The structures are as follows : The distal surface of the 

 retina is bounded by a single layer of cells (PI. 7, fig. 13, 

 D. 8.), the distal cells of Hesse, and the first type of Patten's 

 outer ganglionic cells. They are somewiiat regularly placed 

 so that an epithelial-like layer is formed. The outer ends of 

 these cells, which are directed towards the septum, are broad 

 and bear cilia-like processes, so that a space exists between 

 septum and cell-layer, which is crossed by the nerve-fibres 

 from the distal nerve and filled by the processes of the distal 

 cells, Avhich for the most part do not reach the septum (this 

 may be caused, however, by breakage of the fine processes 

 durinsT fixation). The cells are cvlindrical, transverse sections 

 cut in the plane of the retina, being perfectly circular (PI. 7, 

 fig. 16, D.S.). Their lower ends are rounded, and in some 

 cases appear to terminate in a short pointed process. This, 

 however, could not be followed far, and I have only seen it in 

 some maceration preparations. 



The cell contents are finely granular. Dark-staining 

 granules (basal granules) are present at the bases of the cilia- 

 like processes (PI. 7, fig. 13), and these sometimes produce 

 the appearance of a dark-staining edge. There are also 



