ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
679 
absolutely necessary to add the soda solution better results are thereby 
obtained. 
With regard to the necessary addition of alkali or acid to the mor- 
dant, the author points out that there is some connection between this 
fact and the formation of acids and alkalies by certain bacteria : for the 
acid-forming bacteria required the addition of alkali, and the alkali- 
producers the addition of acid before they would stain. 
Another interesting observation made by the author was that some 
bacteria possess tufts of flagella, and these are well demonstrated in the 
photographs accompanying this paper. 
Fig. 82. 
Staining Spinal Cord with Naphthylamin Brown and Examining 
with the Dark-field Illumination.* — For preparing serial sections of 
spinal cord, Herr O. Kaiser finds the following procedure useful. The 
sections imbedded in celloidin are removed from the knife with filter 
paper and placed at once in the following staining solution : — Alcohol, 
100 ; water, 200 ; naphthylamin brown, 1. The sections folded up in 
filter paper are arranged in a glass cap- 
sule, as shown in the figure. Herein they 
may remain for some hours to two days. 
The sections when removed from the 
staining fluid are washed with 96 per cent, 
spirit and then placed on the slide. 
When the excess of alcohol is removed 
the sections are fixed to the slide by blow- 
ing ether vapour over them through a 
pipette bottle. As the sections become 
a little creasy, a few drops of absolute 
alcohol are run over them, after which the 
slide is placed in origanum oil, then in 
xylol, and the specimen finally mounted 
in balsam. Naphthylamin brown colours 
the chromophilous cells dark brown, while the chromophobous cells 
appear as bright objects on a dark ground. The blood-corpuscles are 
of a coppery red hue. In order to distinguish between the grey and 
white matter, it is necessary to use the dark-field illumination. This 
is easily done' by inserting a stop in the Abbe condenser. The white 
substance now shows up as a bright yellowish-brown, while the grey 
matter is dark brown, all the finer details being quite clear. The 
blood-corpuscles are of a bright scarlet hue, so that the vessels seem 
injected. 
Staining the Endings of Motor Nerves with Methylen-blue.j* — Prof. 
A: S. Dogiel, after recommending this method, and alluding to the usual 
procedure, states that it may be simplified and improved in the following 
manner. The tissue removed from living or recently killed animals is 
placed on a slide or in a watch-glass containing some drops of aqueous or 
vitreous humour. To this are added two to three drops of a 1/15 to 
1/16 per cent, solution of methylen-blue made up with physiological salt 
solution. In this condition the preparation is left exposed to the action 
* Zeitschr. f. Wiss. Mikr., vi. (1889) pp. 471-3 (1 fig.), 
f Arch. f. Mikr. Anat., xxxv. (1890) pp. 305-20 (1 pi.). 
