90 W. J. DAKIN. 



in the rod-cells (PI. 7, fig. 13, cdU li.). In a memoir on 

 Pecten (44) I made the statement that this was probably the 

 true condition, and I find that Schreiner in his text-book on 

 histology (38) has done the same. The latter author refers to 

 the axial fibre as a neurofibril, a structure wliich has risen in 

 importance since Apathy's work in 1897 and about which 

 very much has been written, chiefly on the continent, in the 

 last few years. I believed that the thick neurofibril easily 

 seen in the rods divided into numerous delicate, more 

 elementary fibrillae in the rod-cells, a view rendered more 

 probable by the fact that whilst the contents of the latter are 

 uniformly distributed, filling the cell, the protoplasm of the 

 rods is usually aggi-egated in the middle. 1 couhi not at that 

 time, however, find proof of this in Pecten, although Hesse 

 stated that sometimes he had seen more than one fibre 

 present. 



Usually the axial fibre is thickest and stains most darkly in 

 the upper half of the rod, though sometimes the whole length 

 in the rod is much the same in appearance. 



It begins to disappear a little below the line of junction 

 with the rod-cells, but again sometimes extends quite as 

 distinctly a little above this. This disappearance, or partial 

 disappearance, is due to the separation into delicate branches 

 which extend right through the rod-cell (PI. 7, fig. 13, 

 B., B.C.). 



The separation is irregular, aud sometimes one fibril is left 

 much thicker and may be followed easily through the rod- 

 cell : presumably this feature gave rise to Patten's view. 



The point of separation of the axial fibril of the rods into 

 finer fibrillte varies even in the same section, and in rod-cells 

 situated near the margin of the retina (young rod-cells) the 

 axial fibre may often be seen as thick and distinct as in the 

 rods. In macerations in chloral hydrate solution or chromic 

 acid and also in teased fresh material the axial fibril is seen 

 as distinctly as in stained sections. 



It is rather thick and quite stiff like a bristle in these 

 preparations, never having normally the snaky course 



