Nuclei Tuberis Laierales and the Ganglion Opticum Basale. 39 



Explanation of Illustrations. 



Figs. 1 to 35 and lA to 35A have been prepared in the following manner: 

 The entire section was in each case projected at a magnification of ten 

 diameters, and the outlines together with as many details as possible were 

 drawn in pencil; even bloodvessels, tears in the section, particles of detritus, 

 etc., were drawn in so as to serve the purpose of orientation. Under the 

 microscope at the same magnification (ten diameters) the drawing was 

 completed, with the occasional aid of higher magnification. (Of course the 

 drawings were not begun until I had a clear idea of the location, extent, 

 cell character, and relations of the various cell groups.) This completed 

 drawing is not used for publication but serves as the basis for two others. 

 In the first place an outline drawing is made (by tracing) and the various 

 structures labeled (Figs. lA to 35 A) ; in these drawings a rectangular area 

 is indicated which contains the region in which we are interested. A second 

 series of drawings (Figs. 1 to 35) are traced from that portion of the original 

 included within the rectangular area, and the details filled in, under control 

 of the microscope. Finally these two series of drawings have been repro- 

 duced in parallel columns; in order to do this the outline drawings have 

 been more greatly reduced in size than the detailed drawings, the resulting 

 magnification being indicated in the explanation of each plate. Figs. 1 to IS 

 have been so much reduced that they should be examined with the aid of a 

 hand lens; the cells of the nuclei tuberis laterales are especially difficult to 

 recognize without such aid. 



It is important to understand just what these drawings are intended to 

 illustrate. The outline series (Figs. lA to 35A) needs no explanation, except 

 the statement that the size and relations of the structures shown have 

 been accurately reproduced. In the other series (Figs. 1 to 35) the distri- 

 bution of each cell group is accurately shown, each being indicated by one 

 type of cell which may be distinguished in all drawings from the cells of 

 all other cell groups; thus different cell groups may be distinguished when 

 their cells are intermingled, and it is thereby possible to reproduce the 

 actual extent of each cell type without resorting to an arbitrary boundary. 

 On the other hand in order to indicate differences in cell type it has been 

 necessary to make the cells much larger than they appear at such a low 

 magnification, and this in turn involves a reduction in the number of cells. 

 However, the relative density of each cell mass in its various portions is 

 shown, and the relative size of different cell types has been maintained, 

 although this difference in size has in some cases been somewhat exag- 

 gerated in order to make it more obvious. For a true picture of each cell 

 type one must study Figs. 38 to 58, in which each cell type has been 

 reproduced exactly as it appears. 



The exact cell size and distance between the cells of the nuclei tuberis 

 laterales and the basal optic ganglion, as well as that of the surrounding 

 cell groups, has been reproduced exactly in Figs. 36 and 37, which also show 

 the different cell types as they appear at a relatively low magnification. 

 These two illustrations (Figs. 36 and 37) will be explained on the pages 

 facing them. 



