680 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
reaction, and those in which the colour was discharged an acid one. 
This was confirmed by chemical experiment, for by adding an alkali 
the solution became green, while the addition of acids removed this 
colour. In this jequirity solution, therefore, there exists a means 
of distinguishing between bacteria which form acids and those which 
form alkalies. 
The results of the addition of various substances, agar, gelatin, 
pepton, glycerin, alone or in combination and with neutral or alkaline 
reaction are exhibited in two tables. The most favourable results seem 
to have been obtained from the simple solution of jequirity with neutral 
reaction, and from an alkaline 
solution to which 2 per cent, of 
pepton had been added. 
Reichel’s Apparatus for Filter- 
ing Fluids containing Bacteria.* 
— Herr Reichel describes an ap- 
paratus which he has devised for 
filtering fluids, and which is ex- 
pressly intended for bacteriolo- 
gical work. It consists of a glass 
vessel somewhat resembling an 
inverted funnel. The body B is 
intended for the receiver, while 
from the bottom projects upwards 
the tube D, and from the neck the exhaust-tube C. Into the neck fits 
the porcelain filter A. The tube D is intended for the evacuation of the 
filtrate or removal of small portions for test purposes. When in use, 
the air is exhausted by means of an air-pump attached at C, the orifices 
at A being carefully plugged with cotton-wool. 
Organisms of Nitrification and their Cultivation.! — M. Winograd- 
sky, who at one time ascribed the nitrifying faculty to a single species of 
bacteria called Nitromonas, has by later investigations satisfied himself 
that morphological differences exist in these organisms, and they are now 
classed together in a group of “ Nitrobacteria,” the common characteristic 
of which is the oxidation of the ammoniacal nitrogen. The bacteria 
were cultivated on the following medium, devised by Kiihne,! an d 
modified by the author : — Commercial silicate of soda is diluted with 
thrice its volume of water, and then 100 ccm. is thoroughly mixed with 
50 ccm. of dilute hydrochloric acid. The mixture is dialysed for 24 
hours in running water, and then for two days in distilled water fre- 
quently renewed. The dialysis is completed when the fluid remains 
quite clear on addition of silver nitrate. The solution may now be 
sterilized by boiling, and preserved in flasks closed with cotton-wool. 
The second solution is composed as follows : — Ammonia sulphate, 
0 • 4 ; magnesium sulphate, 0 * 05 ; potassium phosphate, 0*1; calcium 
chloride, trace ; sodium carbonate, 0 • 6-0 * 9 ; distilled water, 100. The 
sulphates and chloride are dissolved and sterilized together, as also are 
* SB. Phys.-Med. Gesellscli. zu Wiiizburg, 1801, pp. 44-7 (1 fig.). 
f Ann. de l’Inst. Pasteur, 1891, p. 92. See Centralbl. f. Bakteriol. u. Parasi- 
tenk., ix. (1891) pp. 603-5. % See this Journal, ante , p. 130. 
