• ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 233 



variations in speed, it is regulated satisfactorily. While cutting serial 

 sections the assistant never has to touch the fly-wheel with his hands, as 

 he is able merely by using the foot-control to ruove the paraffin-block 

 a fraction of an inch at a time, as well as being able to cut sections one 

 by one if necessary. In this manner colloidin sections have been cut 

 with a slanting knife. Much time and expense are saved by this device. 



(4) staining- and Injecting. 



Simple Method for Double-staining Sporulating Bacteria.* — C. 

 Botelho recommends the following procedure : — Dissolve light green 

 4 grm. and acid-fuchsin 2 grm. in a solution of glacial acetic acid and 

 distilled water, 50 c.cm. of each. The material, with a drop of water, is 

 placed on a slide and fixed by heat. The film is then covered with 

 the stain and heated to vaporization. This procedure is repeated three 

 or four times. When cool wash with distilled water. Dry and examine. 

 Spores are stained red, the bacilli green. 



New Method of Staining the Tubercle Bacillus.|— C. Cepede recom- 

 mends the following procedure : — The sections or smears are first 

 treated with carbol-fuchsin, heated for five minutes. They are then 

 immersed in the following solution for two to three minutes : — 

 Methylen-blue in excess ; lactic acid, 40 c.cm. ; distilled water, 160 c.cm., 

 1 part ; alcohol 95 p.c, 4 parts. The preparation is then washed in tap- 

 water, and if any red remain the blue solution must be reapplied. Then 

 dry and examine. In urine the technique is slightly different. Before 

 colouring with fuchsin the preparation is treated with a soda solution 

 to which 5 p.c. alcohol has been added. This removes the fat from the 

 smegma bacillus, and prevents confusion. 



C5") Mounting', including- Slides, Preservative, Fluids, etc. 



New Counting Chamber.| — J. W. Cropper read a note on a 

 " New Counting Chamber for the Enumeration of Protozoa and other 

 Organisms" (from the Marcus Beck Laboratories, Eoyal Society of 

 Medicine). The chamber was designed on the principle of the ha3mo- 

 cytometer, but with a considerably larger area — namely, 5x5 mm. — 

 of the platform rialed in squares, the latter also being increased in size. 

 For various practical reasons the depth of the chamber was retained as 

 yV mm. as in the older chambers. Thus the organisms or cells in a 

 comparatively large volume — namely, 2*5 c.mm. — could be counted, and 

 in cases where the number present was scanty it was possible to count a 

 sufficient number of organisms to minimize the statistical errors which 

 were inseparable from a small count. The size of the smallest squares 

 had been so arranged that they occupied the central half of the diameter 

 of the field of the microscope, using a ^-in. objective and a x 7 eye- 

 piece, this permitting a rapid count being made. In cases where the 

 organisms or cells could be easily recognized with a low-power magnifica- 



* C.R. Soc. Biol. Paris, Ixxxi. (1918) pp. 183-4. 

 t Comptes Rendus, clxvi. (1918) pp. 357-9. 

 t Lancet, March 2, p. 387. 



R 



