EXPLANATION OF FIGURES 
All drawings are made from the brain of the carp, Cyprinus carpio L. The 
individual specimens from which these are made range from 15 to 30 cm. in length 
for the Golgi preparations; 25 to 40 em. for those prepared with toluidin blue and 
the method of Ramén y Cajal, and 35 to 60 cm. for the Weigert preparations. 
Figs. 1 to 4 were drawn with the use of a dissecting microscope; for all others there 
were used a camera lucida and Zeiss microscope with the following objective and 
ocular combinations: compensating ocular 4*, objective A*; compensating ocular 
8, objective A*; ocular 2, objective AA; ocular 4, objective AA; ocular 6, objec- 
tive AA; compensating ocular 6, objective AA; compensating ocular 4, apochro- 
matic objective 16 mm.; compensating ocular 4*, apochromatic objective 8 mm. ; 
compensating ocular 18, apochromatic objective 4 mm. 
On all figures from longitudinal sections an arrow (—) is placed always pointing 
rostrad. Where a double pointed arrow (<~—) appears after the name of a tract 
it signifies that the tract in question contains both ascending and descending fibers ; 
the name used on the figures is, however, always that of the descending tract. 
All figures from the Weigert or toluidin blue method are from transections; in 
the case of the latter every cell appearing in the section is drawn in with a camera 
lucida in order to obtain the proper grouping. 
The eight diagrams, figs. 125, and 136 to 142, consist in each case of a basal dia- 
gram, the same in figs. 125 and 141, and in figs. 136 to 140, 142; to which is added in 
one or more different colors, the fiber connections. The two different basal dia- 
grams are made from series of adjacent sections by the Weigert method, sagittal 
in the case of figs. 125 and 141, frontal in figs. 136 to 140, 142. These are drawn 
with tke aid of a camera lucida, a Zeiss comp. oc. 4*, and objective A*, and are 
superimposed in such a way as to bring as many as possible of the structures to be 
considered into one figure. The relations are not, of course, accurate for any one 
givenplane. The fiber tracts are represented by simple lines showing the course 
of each tract and its connections. The tracts so represented, are not, of course, 
equal in respect to number of fibers; some, such as the lateral forebrain bundle, 
are composed of an enormous number, while others, such as the tr. preoptico- 
habenularis, pars posterior, contain only a few. 
255 
