22 Edward F. Malone. 



teristic cell type. A reference to Fig. 36 will serve as an introduction 

 to the further consideration of the differences in cell character. On 

 comparing the cell character of the nuclei tuheris laterales of man and 

 macacus (Figs. 39 and 45) with that of the other cell groups shown 

 in the illustrations it will at once be evident that this cell type differs 

 radically from all others except that of the substantia grisea of the 

 third ventricle (Figs. 40 and 46) ; this similarity is of importance, 

 and its significance w'ill be considered when the relationship of the 

 various cell types is discussed. Comparing the cell type of the nuclei 

 tuberis laterales in man (Fig. 39) and in maoacus (Fig. 45) it is 

 evident that aside from the 2>resence of pigmentation in man (of course 

 not to be expected in macacus) there is no essential diiference. The 

 fundamental characteristic of this cell type in both forms lies in the 

 appearance of the cytoplasm, which contains an extremely small amount 

 of Xissl substance in the form of fine granules ; the relation of cell 

 nucleus to cytoplasm in respect to volume is 'also practically the same, 

 although in macacus the cytoplasm is relatively less, a change that is 

 to be expected, as will appear later. In describing the cells of the 

 nucleus ansae peduncularis (p. 18) I pointed out the fact that if two 

 cell groups differ as to the amount of yellow pigment in their cells they 

 will also differ in other respects, and that homologous groups in lower 

 animals (where all pigmentation is absent) will also appear different. 

 Accordingly the presence of densely packed yellow granules in the cells 

 of the nuclei tuberis laterales of man is not the only distinctive charac- 

 teristic of these cells, but is connected with other characteristics, 

 common also to the homologous cells of macacus ; these characteristics 

 involve the appearance of the cytoplasm and make it possible to separate 

 these cells without difficulty from those of surrounding groups. If we 

 study the cell type of the substantia grisea in all four fonns (Figs. 40, 

 46, 51, and 56) we find the cell type practically unchanged, since in all 

 fonns the cells of this group are characterized by the extremely small 

 amount of cytoplasm and relatively large nucleus; in many cells the 

 cytoplasm is almost absent, and one sees only a large nucleus and 

 perhaps one or more cell processes. 



Accordingly the cells of the substantia grisea may be readily separated 

 from those of all portions of the nuclei tuberis Laterales not only 

 through their smaller size, but also through the minute amount of 

 cytoplasm in relation to the size of the cell nucleus; however, on the 

 border line between these two types of cells occur occasionally transi- 



