ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 415 



wheel, 3 x \ in. A handle is inserted in one side, as shown in the 

 diagram, though very little use is found for it. 9. Winged nut, \ in. 

 in diameter. 10. Slot, 2£ x \ in. (fig. 47), in which the bolt of the 

 winged nut slides. This allows the adjustment of the drum to meet re- 

 quirements. 11. Inclined plane, 12 x 6f x \ in. At one end two pegs 

 are placed to engage those shown in fig. 46, A^. 



General Directions : — The only difficulty that will be encountered in 

 the making of the carrier will be to fasten the axle supports squarely 

 in the centre of the drum. Centring the axles may be easily accom- 

 plished by drawing a circle the exact size of the drum on a board, and 

 then, after determining the centre, drill a hole the size of the axle (\ in.) 

 through it. Insert the axle into this hole (fig. 46, E). Drive long brads 

 cr nails at the periphery of the circle as shown in this fig. so as to hold 

 the drum firmly in place when it is lowered. Coat the axle support with 

 glue and press the drum tightly against it. The nails will hold the 

 drum in place, and the axle will be in the exact centre of the cylinder. 

 Glue may serve to fasten the axle permanently to the drum, but the author 

 finds that it does not take a very firm hold of the tin and soon breaks 

 away. This may be overcome by first placing small brads or screw- 

 eyes' (fig. 46, B 1) in the sides of the axle supports and then gluing the 

 disks on as directed above. After the glue has set firmly enough to hold 

 the disks in place solder is run in under the screw-eyes and they are thus 

 firmly fastened to the tin. 



Directions for using : — Cut a ribbon from 8 to 10 in. in length and 

 press one end lightly against the blotting-paper covering the drum. 

 After this the ribbon is wound on the cylinder as it comes from the 

 microtome (shown in fig. 47) by thumbing the edge of the driving wheel, 

 which revolves the drum very slowly (the drum revolves once to every 

 two and a half revolutions of the driving wheel). The winged nut 

 allows the cylinder to be adjusted to the demands of the particular 

 microtome in use. The ribbon is wound spirally upon the drum by 

 sliding the carrier parallel to the knife. AVhen ready to mount, the 

 ribbon is unwound on to the inclined plane which is covered with blot- 

 ting-paper and cut to the desired lengths. 



(4) Staining- and Injecting-. 



Viability of Dried Bacterial Preparations (Stained and Un- 

 stained).*— 0. Thurn has investigated the effects of drying, and stain- 

 ing with different reagents, on slide preparations of various kinds of 

 bacteria. The organisms principally used were micrococci, coli, typhoid, 

 cholera, diphtheria, and yeast. Ordinary methods of drying film-prepara- 

 tions (including the usual rapid drawing three times through the 

 Bunsen flame) had no effect on the viability of the bacteria. With 

 regard to stained preparations, he found the Ziehl carbol-fuchsin stain 

 killed most vegetative forms of bacteria, but spore-staining by Moller's 

 method had no effect (B. mesenterial and B. anthracis). Acetic acid 

 methylen-blue (Neisser's stain) prevented the growth of B. diphtherise, 



* Centralbl. Bakt., lte Abt. Orig., lxxiv. (1914) pp. 81-90. 



