The Microscope. 29 



A New Staining Method for the Central Nervous 

 System.* — Pieces of the nervous tissues are placed for 5 weeks 

 in a mixture of equal parts of a 1 per cent, solution of chloride 

 of gold, and a 1 per cent, solution of corrosive sublimate. 

 Sections are cut in dilute (J) Lugol's solution. (On les coupe 

 alors dans la solution de Lugol diluee (i).) The fibres with or 

 without myaline, the nerve cells and those of the neuroglia are 

 colored blue. In the ganglion cells the nucleus and the nucleo- 

 lus are plainly visible. 



Flagella of Minute Microbes. f — It is not difficult, ssljs 

 Mr. G. F. Dowdeswell, provided that an appropriate, but quite 

 ordinary means be adopted, to demonstrate the flagella of min- 

 ute microbes, for example, the comma forms. The first to do this 

 was Mr. E. M. Nelson, who showed them in 1886, at a meeting 

 of the Royal Microscopical Society. The optical apparatus 

 required are a normal retina, a good objective with a moderate 

 angle of aperture, and a good light. For staining purposes 

 gentian-violet answers as well as any other color, but it is neces- 

 sary to be particular as to the method of mounting. The speci- 

 mens must be mounted in a solution of acetate of potash, and not 

 in balsam. By this method no difficulty will be experienced in 

 demonstrating flagella of miorcbes as small as Bacterium termo. 



A Method of Illumination. — Mr. J. A. Perr}', writing to 

 Science G^ossip, describes a method of microscopical illumination 

 which is simple and said to be very pleasing. It is produced 

 b}^ a disk of ordinary cover glass ground on both sides, and 

 used in the same place and in the same manner as the ordinary 

 black-ground stop below the sub-stage condenser, the marginal 

 rays of light passing unobstructedly around the outer edge of 

 the ground cover glass, producing a different and far more pleas- 

 ing effect than that produced by the ground glass extending over 

 the whole aperture of the condenser, and entirely different to 

 that produced by a ground glass cap over the top of the con- 

 denser. It is a very pleasing mode of illumination on almost 

 all objects usually viewed with a black ground, as well as those 

 objects viewed by direct light. 



* Neurol. Ceutrab. Cf. Bui. Soc. Beige de Micros. 

 tAnnals de Micrographie. Cf. Journ. R. Micr. Soc. 



