70 MORRILL. [VOL. XIV. 
watch glass was used for this purpose. A %% solution of 
methylen blue in normal salt was added in sufficient quantity 
to produce a deep blue color, but not enough to render it 
opaque. Very little of the blue was required. The staining 
fluid was occasionally agitated by forcing air through it by 
means of a medicine-dropper. The temperature was kept 
between 80° F. and g0° F. The best results were obtained on 
the hottest and dryest days in August. A warm plate or 
thermostat was used to maintain the proper temperature when 
needed on cool days. At the end of an hour to an hour and a 
quarter the stain was removed by means of a pipette, and the 
specimens rinsed with normal salt solution to remove excess of 
stain. They were then exposed to the air for ten to fifteen 
minutes, care being taken to keep them moist with normal salt 
solution. At the end of this time the specimens were trans- 
ferred to the fixing fluid, which consisted of a saturated solution 
of picrate of ammonia in distilled water, to which one-third of 
its volume of normal salt solution was added. Two or three 
drops of 1% osmic acid was also added to every 10 cc. of the 
fixing fluid. The osmic acid prevented maceration and black- 
ened the medullated nerve fibers. After treatment with the 
fixing fluid for about an hour and a half, the ampullae were 
transferred to a saturated solution of loaf sugar in distilled water 
for one hour. The syrup was removed from the surface of the 
specimens with blotting paper, and they were placed in a satu- 
rated solution of pure gum arabic in water for fifteen minutes. 
The ampullae were then placed one at a time in a drop of the 
gum arabic solution on the plate of a freezing microtome, and 
after careful orientation were frozen. The freezing was accom- 
plished by means of liquid carbonic acid. The apparatus! 
used was modeled after the one designed by Dr. Mixter of the 
Harvard Medical School. The sections were cut with a plane 
iron mounted between two thin pieces of wood and held in the 
hand. This portion of the work was done as rapidly as possible, 
and even then it was sometimes necessary to refreeze to keep 
it sufficiently hard. 
The sections varied considerably in thickness, but averaged 
1 Manufactured by The Bausch & Lomb Optical Co., Rochester, N.Y. 
