88 GEORGE W. BARTELMEZ 
These observations are based chiefly upon the study of serial 
sections of the brains of Ameiurus and other teleosts, both larval 
and adult, prepared as follows: 
10 series of Ameiurus, fixed with formol-Zenker and stained with toluidin blue. 
and erythrosin; 4 
20 series of Ameiurus, Cajal and Bielchowsky methods; 
10 series of Ameiurus, fixed with formol-osmic-Zenker and acetic-osmic- 
bichromate, stained with iron hematoxylin; 
10 series of larval trout heads, prepared chiefly by the Cajal method; 
100 series of brains of siluroids and cyprinoids prepared by the Golgi method; 
3 series of Ameiurus, Weigert method. 
The brains prepared by the methods of Golgi and Weigert 
were loaned to me by Professor Herrick, who also placed at my 
disposal other series of brain sections, including representatives of 
various species of teleosts in addition to those mentioned above. 
The toluidin blue and erythrosin method was found to be very 
certain in its results and particularly valuable in giving clear 
pictures of cell groups and fiber tracts, as well as showing the 
_ Nissl substance in the cells (figs. 3-9). The fish were decapi- 
tated and bled and the brains dissected out under a binocular 
microscope in normal salt solution. They were fixed in formol- 
Zenker for 2 to 12 hours according to their size, cut in paraffin 
10 uw thick and stained in a 1 per cent solution of toluidin blue 
in water for 12 to 24 hours. The slide was then drained and 
dipped directly into a 0.5 per cent solution of erythrosin in 95 
per cent alcohol and agitated until the sections were red. They 
were then dehydrated rapidly in absolute alcohol, cleared in tol- 
uol and mounted in neutral balsam. 
Under the stimulus of the striking preparations of teleostean 
brains figured by Beccari (07) and Tello (09) I made many 
experiments with the Cajal method and elaborated a technique 
which is sure to give results with larval brains. Only about 10 
per cent of the young adult brains gave preparations that were 
first rate, but 90 per cent were worth study. The following pro- 
cedure may be recommended: 
Fix entire heads of larvae or the brains of adults in acetic alco- 
hol, varying the proportion of acetic acid according to the water 
