Nuclei Tuberis Laterales and the Ganglion Opticum Basale. 13 



and cat) ; the same is trae as to the fusion of the ganglia of opposite 

 sides (definite in man, less so in macacus, barely present in the lemur 

 ajid not always present in the cat.) 



Cell type of the basal optic ganglion. 



It is not my intention to attempt to give in words the characteristics 

 of the cells of the basal optic ganglion which have been already satis- 

 factorily shown in the illustrations. I shall confine myself to pointing 

 out the fundamental characters of these cells, and when we have thus 

 become familiar with the main features of the cell picture we shall be 

 in a position to discuss the relations of these cells to those of other 

 groups. The water color reproductions of the cells of the basal optic 

 ganglion, and of all other cells thus illustrated (Figs. 38 to 58), were 

 all drawn from cross-sections of the brain. In Series D of man, in 

 which the plane of section differs widely from that of a cross-section, 

 I have been unable to observe any important difference in the appear- 

 ance of the cells of the basal optic ganglion, and it is my opinion that 

 the plane of section does not affect to any appreciable extent the appear- 

 ance of the majority of these cells. The cells of the basal optic gang- 

 lion and of all other groups illustrated are as characteristic in Series D 

 a.s in Series AC. However, I have not made a careful enough study 

 of this point to state definitely that the cell character is absolutely 

 unaffected by differences in the plane of section. The cells of the basal 

 optic ganglion in all four animal forms (Figs. 38, 44, 50 and 55) are 

 large polygonal cells which possess very coarse processes. These pro- 

 cesses, as is shown in Fig. 37, form an intercellular feltwork; under 

 low power one would hardly suppose that this feltwork was composed 

 of cell processes, and the ganglion appears to be characterized not only 

 by its typical cells but also by the presence of a distinctive intercellular 

 substance. These processes are practically colorless, and are in Fig. 

 37 represented as blue because at this magnification they could not be 

 shown in any other manner. The cell processes in Figs. 38, 44, 50 and 

 55 are not as long as they appear in the actual preparations. Another 

 fundajnental character of these cells is the distribution of the Nissl 

 substance, nearly all of which is massed on the periphery of the cell ; 

 this peripheral distribution is not equal in all portions of the periphery, 

 since the depth is much greater at certain points, and at other points 

 of the periphery the iNrissl substance may be almost entirely absent. 



