244 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
position of the screws arranged as in fig. 41. From what has been said, 
it will be gathered that the microtome is well adapted for celloidin 
sections, which may be cut as thin as 10 micromillimetres. 
Groot’s Improved Lever Microtome.* — M. J. G. de Groot states 
that the advantages of his recently improved microtome are that the 
instrument is very strong ; the knife cannot wobble, and may be fixed at 
any angle. Movement is imparted by the oscillation of a lever. The 
paraffin block slides easily and smoothly under the knife ; it is easy to 
fix or unfix the object. The thickness of the section is easily regulated. 
The size of the section may amount to 4-5 cm. square. Celloidin sections 
are also easily cut by this machine ; it is only necessary to immerse the 
block in paraffin so that it can be fixed to the object-holder in the usual 
way. 
C4) Staining- and Injecting. 
Chrome -silver Impregnation of Formalin-hardened Brain.f — Dr. J. 
S. Bolton has obtained excellent results from brains hardened in forma- 
lin for periods of 5 weeks to 12 months according to the size. Pieces 
of cortex 1/8 in. thick with a base of about 1/4 in. are then immersed 
in 1 per cent, ammonium bichromate for a few hours to five days. The 
pieces are then rinsed in distilled w T ater and placed in a bath of 1 per 
cent, silver nitrate for 16-24 hours or even longer. The pieces 
are next hardened by immersion in 60 per cent, alcohol for a few 
hours, and having been mopped up with blotting paper, imbedded without 
soaking in paraffin. The sections are placed successively in methylated 
spirit, absolute alcohol, chloroform and xylol, and mounted in xylol 
balsam without cover-slip. 
The author also states that for some time he has passed the Golgi 
sections into water and developed and fixed them by the method of 
Kallius, afterwards treating them as above and mounting under a cover- 
slip. 
Staining Flagella of Bacteria with Orcein.f — Prof. Bowhill stains 
flagella in the following way. Two stock solutions are required, one a 
saturated alcoholic solution of orcein (the solution improves by keeping 
for about 10 days) ; (2) a 20 per cent, solution of tannin. When re- 
quired for use the foregoing are mixed in the following way : — 15 ccm. of 
orcein solution, 10 ccm. of tannin solution, and 30 ccm. H 2 0, and then 
filtered. 
Young agar cultures are recommended as affording the best results. 
The film is prepared in the usual way from a suspension in distilled 
water, and the cover-glass dropped film side downwards on the orcein 
solution in a watch-glass. The fluid is then gently warmed, and the 
preparation allowed to float for 10-15 minutes. The cover-glass is 
then washed and examined in water. If satisfactory, it is dried and 
mounted in balsam. The bacteria are stained a bluish-purple colour, 
the flagella being of a somewhat paler hue. A list of nineteen bacteria 
stained by this method is given, among them being Sp. cholerse asiaticse , 
B. typhi abdominalis , and B. coli communis. 
* Ann. Soc. Beige de Microscopie, xxii. (1897) pp. 77-80 (1 fig.), 
t Lancet, 1898, i. pp. 218-9. f S.A. Hygienischen Rundschau 1898, No. 3. 
