408 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
gration, each structural element being separated from its neighbours, 
with little or no corrosion of the wall. 
Cleaning Diatoms.^ — Mr. Edward S. Nott recommends that— 
(1) The material be completely disintegrated by continued boiling 
in a solution of sal soda. 
(2) The disintegrated material should be sifted in a sieve made of 
bolt-cloth, removing all the fine earths and broken forms. 
(3) The remainder may have the greater part of the sand removed 
from it by revolving it in an evaporating dish with water. 
(4) The material, now mostly diatoms, should be boiled in acids : 
first, in muriatic, then wash ; second, in nitric, then wash, and sometimes 
boil also in sulphuric acid. 
(5) After washing all traces of acid away, boil once more in a 
solution of sal soda, wash, and sift in a fine sieve of bolt-cloth. 
The object is to remove all the debris and waste material before 
using the acids, as the result will be better and the expenditure of time 
and labour less. The stock should be kept in alcohol, and in mounting, 
the best distilled water should be used. 
C4) staining- and Injecting. 
Methylen-blue Staining for Nerve-endings. f — The examination of 
nerve-endings by staining with methylen-blue, a method invented by 
Ehrlich, has received, since its introduction, considerable attention at the 
hands of physiologists, owing to the comparative simplicity of the 
procedure, and the satisfactoriness of the results — results quite equal to 
those obtained by the silver nitrate and gold methods. The method as 
recommended by Prof. S. Mayer, consists of two distinct parts, the 
first of these being the treatment with the blue pigment, the second that 
of its fixation by means of picrate of ammonia. The methylen-blue 
solution is made by dissolving 1 gram of the pigment in 300-400 ccm. 
of a half per cent, salt solution. The picro-glycerin solution is com- 
posed of a cold saturated solution of picrate of ammonia, diluted with an 
equal volume of pure glycerin. 
The animals are injected through a blood-vessel with the blue solu- 
tion, or pieces of fresh tissue are soaked in the solution, or the animal 
may be immersed alive in the fluid without danger to life. 
Small pieces of the object are then immersed in the picro-glycerin 
and are at once ready for examination. If found suitable for a permanent 
preparation the cover-glass can be fixed down with a mass composed of 
equal parts of wax and resin. 
If found desirable the injected or impregnated preparations may be 
kept for some time in the picro-glycerin. 
The effect of the second reagent is to alter the colour of the stained 
parts, all shades of red, brown, black being seen in the axis-cylinders 
and the non-medullated tsrminal nerve-expansions. This disadvantage 
is compensated by the stain being fixed and the preparation cleared up 
at the same time, advantages not counteracted by any considerable 
changes in the tissues. 
* Proc. Amer. Soc. Microscopists, xi. p. 149. Amer. Mou. Micr. Jourii., xi. (1890) 
p. 31. t Zeitschr. f. Wiss. Mikr., vi. (1889) pp. 422-38. 
