28 



put up on end to dry and afterwards passed three or four 

 times through the flame of a spirit lamp, to set the film. 

 A little of the dye is filtered through some fine filter paper 

 into a watch glass, and the cover glasses, with the film down- 

 wards, are floated on it. They are left for half-an-hour or 

 more, according to the dye used, are then taken off with 

 platinum forceps, washed in water, then in diluted acetic acid 

 (i per cent ), to take out any superfluous stain, again washed 

 in water, and put on end to dry. Next they are 'mounted 

 in Canada Balsam, and are fit for examination under the 

 microscope. Stained specimens are best seen with a large 

 diaphragm and much light. 



To examine Bacteria in tissues, sections must be cut 

 with a freezing microtome, and treated as above. There 

 are other and more elaborate methods of preparation, but 

 as I fear I have already trespassed too long on the patience 

 of the Society, I will refer you for them to " Magnin's 

 Bacteria," by Sternberg, to Klein's " Micro-organisms," to 

 the works of Pasteur, and to the article by Watson Cheyne 

 in the International Health Exhibition Handbooks on Public 

 Health Laboratory Work. 



