180 RALPH EDWARD SHELDON 
stronger fluid, changed each week. From this point on the 
method is similar to the one first outlined; viz., dehydration, clear- 
ing, embedding in paraffine, etc. Medullated fibers and nerves 
stand out very distinctly after the use of thismethod. Other 
methods of decalcification were tried but, as Herrick (’97) points 
out, the Weigert method will not ‘take’ after any of the ordinary 
processes of decalcification. Professor Herrick was kind enough 
to loan me, in addition, a series of transverse sections through the 
adult carp brain, stained by the Weigert-Pal method. 
IT. Chloral hematoxylin and eosin method 
Entire carp, 1 em. in length, decalcified. 
Two series transverse sections. 
Three series sagittal sections. 
Two series frontal sections. 
ITI. Toluidin blue method 
The only fixing agent which gave uniformly good results with 
this stain was Graf’s chrom-oxalic for twelve hours. This method 
was used for the differentiation of areas and the cytological struc- 
ture of the nerve cells. 
One series transverse sections. 
One series sagittal sections. 
One series frontal sections. 
IV. vom Rath method 
This was used for the unmedullated tracts, particularly in the 
olfactory bulbs, where two series of transverse sections were made. 
The method followed is that given by vom Rath (’95). This 
consists of fixation in the following solution for three days; satu- 
rated aqueous solution of picric acid, 200 ec., 10 per cent platinie 
chloride, 10 ce.; 2 per cent osmic acid, 25 cc.; glacial acetic acid, 
2 cc. Next the specimens are placed in methyl alcohol for 15 
minutes, 0.5 per cent aqueous solution of pyrogallic acid for two 
days, dehydrated for two weeks in the dark, cleared in carbol- 
