142 JouRNAL OF COMPARATIVE NEUROLOGY. 
fixed with 10% formalin and the sections are made by either 
paraffin or celloidin technique according to the usual procedure. 
The sections are first treated for several minutes with dilute hy- 
drochloric acid, and then transferred to the blue solution where 
they remain for 24 hours. If the section is over-stained, it 
_may be decolorized with 1% potassium permanganate for a 
second, and the further oxidation is stopped by transferring the 
section into dilute hydrobromic acid. The preparation thus 
stained brings out the structures described below. 
Unless otherwise mentioned, the following description is 
based on the observations of cells from the spinal cord of the 
dog. <A careful study of these preparations shows that the 
nerve-cell-body, as well as dendrites, are stained intense blue, 
while the axone appears stained alight blue. The neurokeratin 
in the medullary sheaths, as well as neuroglia fibers stain bluish 
black; the former being more intensely stained. The blood 
vessels and nuclei of their walls, as well as the neuroglia nuclei 
stain faintly blue, and may easily be distinguished from the 
others. The terminals of the axones stain more faintly than 
the axones near their origin from the cell-body, although some 
of the contents of the nerve terminals or neurosomes stain an 
intense blue. Thus my technique brings out the several struc- 
tures at once in different tones, and enables us to analyze the 
material forming the grey matter. 
As Fig. 1 shows, there are a large number of the medul- 
lated nerves which were cut in different planes. In all cases we 
can distinguish these fibers from their surroundings by utilizing 
the fact that the outer layer of the medullated sheath contains 
well marked neurokeratin which stains an intense black. A 
large numberof the dendritic branches are also found inter- 
mingled with the medullated nerve fibers just mentioned. 
These dendritic branches are also cut in various planes and are 
distinguished from the axones by the fact that they are desti- 
tute of the medullated sheaths and at the same time they are 
densely surrounded by the neurosomes. If we examine the 
cross-section of a dendrite, a large number of the granules 
which surround its circumference are easily observed. Another 
