252 BOTANICAL MICROTECHNIQUE. 



pose one need only gently warm the preparation until the 

 balsam becomes fluid, remove the balsam from the raised 

 cover-glass with xylol, and finally wash off the xylol with 

 alcohol. 



It may be remarked, finally, that Bacteria fixed in the 

 above manner may be preserved in this condition for an 

 indefinite time without harm, if they are protected from 

 dust and moisture by being wrapped, for example, in filter- 

 paper. 



461. To remove the strongly staining substance from the 

 red blood-corpuscles, in preparations from the blood, Gun- 

 ther (I, 63) recommends rinsing the objects, fixed in the 

 usual way, in 1-5$ acetic acid. The stainable haemoglo- 

 bin is thus extracted from the red corpuscles, and a large 

 part of the blood-plasma is washed out of the preparations, 

 leaving the Bacteria unchanged. Preparations which give 

 no satisfactory results with this method, on account of hav- 

 ing been kept dry for a long time, have been treated by 

 Giinther with a 2-3^ solution of pepsin, with the best re- 

 sults. 



b. Other Fixing Methods. 



462. Since certain inequalities can hardly be avoided with 

 the fixing methods described above, H. Moeller (II, 274) 

 has proposed fixing the air-dry preparations with absolute 

 alcohol, instead of heating them ; he leaves them in this fluid 

 two minutes. 



463. A. Fischer (II) demonstrated the noteworthy fact 

 that artificial appearances often arise, especially when prepa- 

 rations are allowed to dry, which are chiefly the result of 

 plasmolysis of the bacterial cells (cf. 428). As Fischer has 

 shown, the Bacteria are plasmolyzed by solutions of pretty 

 slight concentration. In general a i$ salt solution is suffi- 

 cient to produce plasmolysis in most Bacteria. Fischer (II, 

 73) recommends the use of a io# solution of lactic acid for 

 fixing Bacteria, which does not prevent subsequent staining 

 with alcoholic solutions of aniline dyes. 



464. Besides, the fixing methods used for higher plants 



