7G W. .1. DAK IN. 



regarded by ]^atten as both belonging to the septum. In 

 preparations stained by Mallory\s method the blue connective 

 tissue is brought out very distinctly against the retina, whose 

 elements are stained red, and hence both septum and nerve- 

 sheath can be easily followed. In some sections there appears 

 to be a delicate concentric striation in the septum, but this is 

 all the structure to be made out. The distal branch of the 

 optic nerve penetrates the septum, the fibres boring through 

 separately. 



The retina has been divided into several layers by previous 

 writers, but anatomically as well as for purposes of description 

 it will be better to consider it as made up of two layers only: 



(1) The outer layer of distal sense-cells with their inter- 

 stitial supporting cells (PI. 6, fig. 1, D. S.; PI. 7, fig. 18, 0. 1, c). 



(2) The inner layer of rod-cells and their continuations 

 the rods, together with interstitial supporting cells (PI. 0, 

 fig. 1 ; PI. 7, fig. 13, B. C. and I. I.e.). 



A table is appended (p. 77) giving the synonyms that have 

 been used, Avhich shows also the gradual changes that have 

 taken place in our knowledge of these structures. 



Hensen (13), as will be seen from the table, placed all the 

 cells present in the retina distally to the rod-cells and rods 

 in one category, called this stratum the "first cell layer/' and 

 said it was composed of one or two layers of spindle-formed 

 cells, whose contours were not very distinct. The layer of rod- 

 cells was called the " second cell layer " and the nuclei of 

 the inner interstitial cells considered to be their nuclei. 



Patten found that the outer cells of Henseu were not all of 

 the same shape. He supposes, however, that physiologically 

 they are alike and calls them all outer ganglionic cells. Of 

 these he described three types, one of which had broad ends 

 bearing many fibrous processes which penetrated the septal 

 membrane and became continuous with the nerve-fibres of 

 the distal branch of the optic nerve. 



One of his most important discoveries was the finding of 

 the interstitial cells of the rod-cell layer, which he termed 

 "inner ganglionic cells" (PL 7, fig. IS, 1. 1, c). Only the 



