No. I.] EPITHELIUM OF MUSTELUS CANIS. 71 
about 50“. They were removed from the plane iron with a 
small camel’s-hair brush and transferred to dilute glycerine, to 
which sufficient picrate of ammonia solution had been added to 
give it a yellow color. 
The sections were easily straightened out by means of a 
brush or needles with the aid of a Leitz dissecting microscope, 
and the best ones removed to slides and mounted in dilute 
glycerine with a trace of picrate of ammonia. The specimens 
kept very fairly and bore transportation well. If desired, the 
cover glass can be cemented on with zinc white or with a mix- 
ture of equal parts of hard paraffin and, turpentine free, Canada 
balsam applied warm with a brush. My best preparations kept 
for several months without marked deterioration when no 
cement was used. The cell outlines are much sharper when 
the preparation is first mounted. The cells seem to swell in the 
glycerine and become more transparent, which often causes the 
nerve fibers to appear more distinctly. The preparations vary 
greatly under what appear to be exactly the same conditions. 
This may be due to different physiological conditions of the 
tissues, which it is as yet impossible to determine. As with 
the Golgi method, there are great variations in the good prepa- 
rations, some showing one detail much better than others. It 
is not difficult, however, to make out all of the main points 
of peripheral nerve distribution in nearly every well-stained 
preparation. 
It was found that if the tissues were nearly dead before being 
placed in the stain, or were allowed to remain too long in the 
stain, or the temperature was too high during the operation, 
isolated epithelial cells were deeply stained, or numerous deeply 
stained granules appeared about the base of the hair cells or 
over their surface. The nerves in this case often appeared as 
rows of disconnected deep blue beads. If too strong a solution 
of the methylen blue was used, varicosities were numerous 
along the course of the nerve fibers, and cells were also stained 
deeply. A dilute solution of the stain seems to act physiologi- 
cally, and the tissue is killed and fixed by the picrate of ammo- 
nia solution. When both cells and nerve fibers are deeply stained 
it is impossible to satisfactorily determine their relation, just as 
