94 W. J. DAKTN". 



reduced, and wliich bear practically no rods, tlionpfli the 

 axial fil)ril, wliich is very distinct, appears to extend a little 

 way below the psendo sieve-membrane. I believe that this 

 region is occupied by young rod-cells and rods, and it can be 

 seen how the rod is a gradual product of the rod-cells, as the 

 appeai-ance of the former in other parts of the retina naturally 

 suggests. The gradual increase in size of the rods at the 

 junction of the marginal and the central rod-bearing region 

 is well marked. Probably the former region does not play 

 any active part in vision at all. 



Hensen called this area the " Retinawiilste," because of the 

 folded appearance in sections, and Hickson's figures also 

 show the retina in this form. I have found the same condition 

 after several fixatives, including Von Ratli's fluid and Bethe's 

 fixative for methylene blue. It is due to contraction, and is 

 not normal. 



The inner interstitial supporting cells (PI. 7, fig. 

 13, T. L c.) have already been referred to several times. 'J'hey 

 lie in close contact with the rod-cells, between which they 

 send their processes, and they are situated not far from the 

 pseudo-membrane (PI. 7, fig. 13, S.m.). Patten was the first 

 to recognise that the nuclei of these cells really belonged to 

 cells lying between the rod-cells ; they had been considered 

 the nuclei of the latter by his predecessors. He figured them 

 correctly as multipolar cells, but fell into error in regard to 

 the nucleus, just as he and most of his successors considered 

 that all the cells between the rod-cell layer and the septum 

 had the same type of nucleus and were physiologically alike. 

 It is quite easy to see in preparations stained with Mallory or 

 iron Inematoxylin that these nuclei resemble exactly those of 

 the outer interstitial cells. There is a considerable difference 

 between them and the large nuclei with distinct nucleolus 

 and chromatin granules, which are present in both the distal 

 sense-cells and the rod-cells (PI. 7, figs. 13 and 16, R. C. n. 

 and D. S. v.). 



The shape of the cells can be best seen in isolated retinas 

 after macerating in -J^^ percent, chromic acid for several days 



