1890] —— Microscopy. 1219 
New Methods of Staining Nerves with Methylblue °— 
Prof. Dogiel says that nerves may be stained with methylblue, not only 
in muscles, but also in other organs, and in a simpler way than that of 
Ehrlich. It is sufficient simply to inject the vessels of the organ with 
a 4 per cent. solution of methylblue in the physiological salt solution. 
The injection is performed immediately after the death of the animal. 
Usually the organ is left 7» sz# until the stain takes effect ; but, if suffi- 
ciently thin, it can be cut out and placed in a drop of aqueous humor, 
and watched under the microscope until the desired effect appears. In 
the first case the organ must be laid bare, and its cavities, if it have any, 
must be opened. The stain may appear in the course of a few min- 
utes, but often only after an hour or two. In the second case the 
conditions are most favorable, not only for staining, but for observing 
the action of the stain and noting the exact time for fixation. 
A simpler method still may be employed for the demonstration of 
nerves in certain organs and tissues, The tissue is taken from the 
animal while living, or just after killing, and placed on a slide or ina 
watch-glass in a few drops of aqueous humor, to which are added 2-3 
drops of a 4-4, per cent. methylblue solution in the physiological 
salt solution. Ordinarily the stain appears in the nerves in 5-ıo min- 
utes; but the time depends much upon the thickness of the tissue. In 
the retina, for example, 2-3 hours or more may be required to brin 
out the nerves of the different layers. The nerves of cold-blooded 
animals stain more slowly than those of warm-blooded ones. 
The fixation of the color may be accomplished conveniently by 
picrate of ammonium, which produces a fine, granular, violet precipi- 
tate with the methylblue, and at the same time renders the tissues quite 
transparent. This reagent also softens the tissue, so that it can easily 
be separated by the aid of needles. Twenty to thirty minutes are 
usually sufficient to fix the stain; but thick tissues may require from 
two to twelve hours. 
It is important that the original blue color be made to pass into a 
violet without the least tinge of green; otherwise the preparation may 
quickly fade. 
The preparation may be mounted in dilute glycerine. 
A saturated alcoholic solution of picrate of ammonia will harden the 
tissue, so that it can be cut in pith or liver, and the sections mounted 
in glycerine, 
5 Dogiel. Arch. f. Mik. Anat., XXXV., 3, 1890, pp. 306-312. 
