50 PATHOGENIC BACTERIA 



teen minutes, the cover-glass is taken up with a fine pair of 

 pointed forceps, tilted to throw off the stain, and at once gently 

 submerged in a saucer of water faintly acidulated with acetic 

 acid ; the washing may be completed in a second or a third 

 saucer, and finally in unacidulated water. The degree of acidity 

 can be arrived at by pouring a few drops of glacial acetic acid 

 into a saucer, inverting it to get rid of the excess, and then fill- 

 ing with water, common or distilled a solution of about .5 c.c. 

 glacial acetic acid to 70 c.c. of water. 



The washing is preferably carried out in this way rather 

 than beneath a stream, as the latter tends to displace the film ; 

 nor is the excess of the dye so well removed by water without 

 the acid. 



Fig. 4. Sheet of lead bent at right angles, with filter-paper folded upon it, and 

 cover-glass stood edgewise to drain without the film coming in contact with the 

 paper. 



After the final washing the cover-glass is allowed to drain 

 and to dry by placing it obliquely with the prepared surface 

 downwards, against a sheet of filter-paper folded at right angles 

 over a piece of lead (Fig. 4). It may be more rapidly dried by 

 pressing between filter-paper, but at the risk of damaging the 

 film and transferring fibers to it. When dry, the preparation is 

 completed by mounting it on a slide with a xylol solution of 

 Canada balsam. 



In a certain few cases (as in agar cultures of the anthrax 



