ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
131 
Tims tube and plate cultivations can bo permanently preserved pro- 
vided that they be prevented from drying. Formalin may also bo used 
for making permanent microscopical preparations. A flat piece con- 
taining the colony is cut out of the gelatin plate with a sharp knife ; 
this is placed on a slide, imbedded in gelatin, and a cover-glass put over. 
The preparation is then put in a formalin-chamber for 24 hours, 
by which time the imbedding gelatin is fixed as well as the rest of the 
specimen. The preparation is then run round with some protective. 
The cultivations may also be stained by placing the pieces from the 
gelatin plates for 24 hours in a weak aqueous solution of fuclisin ; the 
bacteria are deeply stained, while the gelatin is only of a pale red hue. 
Stained preparations may be imbedded and mounted as before, or 
they may be allowed to dry on the slide, and then mounted in Canada 
balsam. 
(3) Cutting-, including Imbedding and Microtomes. 
Leitz’s Microtome.* — In this instrument, represented in fig. 15, the 
preparation is firmly held in a carriage moving vertically in a groove 
Fig. 15. 
WeLaf l^^p^T 34 ° f Micr ° SCOpeS and Accessor y Apparatus, Ernst Lcitz, 
