46 JouRNAL OF COMPARATIVE NEUROLOGY. 
colored castile soap. Allow this to dissolve and filter the mix- 
ture. Place the slide in a crystallizing dish which contains the 
stain. Set the dish on a bath or stove where its temperature 
can be kept at from 55 to 60 degrees C. Four or five hours is 
sufficient to stain the sections, although they do not overstain 
easily. A differentiating fluid is made from go parts absolute 
alcohol and ro parts aniline oil. When no more blue color is 
given off, the sections may be cleared in oil of cajeput, and 
mounted in xylol balsam. So far, I do not find that this mount- 
ing medium affects the stain. 
Nerve cells and their processes should show a rich blue 
stain, and their nuclei a yet darker stain. Fibrous tissue should 
remain unstained, but can be followed with ease, as the tissues 
are well preserved. Fresh tissue is required to begin with, as 
old tissue faz/s of differentiation. Good, clear outlines of gan- 
glionic cells can be obtained, even with an oil immersion lens, 
in the 20 p sections. 
EXPLANATION OF FIGURES. 
REFERENCE LETTERS. 
I. Olfactory nerve. 
II. Olfactory lobes. 
III. Cerebral hemispheres. 
IV. Optic lobes. 
V. Cerebelluin. 
VI. Fourth ventricle. 
VII. Medulla oblongata, 
VIII. Spinal cord. 
TX. Otolith. 
X. Various cranial nerves. 
XI. Pituitary body. 
XII. Lobi inferiores. 
XIII. Saccus vasculosus. 
1. First layer of optic lobe. 
2. Degenerate optic fiber layer. 
3. Optic cell layer. 
4. Deep cell layer. 
5. Deep fiber layer. 
a. Diagonal fibers of deep fiber layer. 
6. Granular layer. 
we aes 
——- 
ee ee ee ee ee ee ee 
eee ee 
a 
ae ae ee ee ee ee a 
