14 , Edicard F. Malone. 



Of course the distribution of the Xissl substance will appear different 

 according to the location of the optical section, and the figures show this 

 to some extent, although they represent to a certain extent a combination 

 of different optical sections. Although minor differences in cell char- 

 acter exist in different animals, the cell group is phylogenetically 

 so old that in the relatively brief interval between man and the cat no 

 changes in cell character have occurred which are sufficiently funda- 

 mental to permit of correlation with the phylogenetic position of the 

 corresponding animals ; this point will be discussed later in connection 

 with the nuclei tuberis, where such a relation between cell character 

 and the phylogenetic position of tlie corresponding animal actually 

 exists. The structure of the cells of the ganglion opticum basale is 

 such as to exclude the possibility of these cells being motor, whereas 

 the large size of the cells probably indicates (as Dr. Donaldson has 

 suggested to me) that they either receive impulses converging from 

 many sources or distribute impulses over an extensive region. 



Separation of the hasal optic ganglion from surrounding cell groups 

 through differences in cell ch^aracier. 



A subdivision of any portion of the nen'ous system based merely 

 upon the splitting up of gray matter through the mechanical agency of 

 fiber masses is, except in certain cases, valuable merely with reference 

 to orientation; such a subdivision should therefore be considered as a 

 crude (although necessary) beginning to be followed by a more careful 

 study of the region involved in which the cell character of the various 

 groups receives careful attention. Moreover it is highly unsatisfactory 

 for an author to state dogmatically that he recognizes the presence of 

 certain cell groups upon the basis of certain differences of cell char- 

 acter, concerning which he is either silent or else treats in a superficial 

 manner; for we are left in doubt as to whether these differences in cell 

 character are really fundamental, and as to the degrees of relationship 

 between the cell characters of various cell groups. When we have de- 

 scribed the location and extent of various cell groups and have made it 

 possible to recognize this by means of a definite cell type, and when we 

 have clearly shown the differences and similarities in cell character of 

 various cell groups, and have pointed out the phylogenetic development 

 and relations of these groups, then and not until then will there be a 

 basis for experimental work which will help solve many important 



