8 



Both fixed and unfixed films rapidly develop 

 moulds in damp and hot climates. Moulds appear 

 as branching threads under the microscope. A 

 certain amount of mould does not much interfere 

 with the utility of films if they are intended only 

 for detecting the presence of parasites, counting 

 leucocytes, etc. 



Unstained films kept for six months or more 

 stain as a rule badly, and are not of much use. 

 Stained films (as we shall see, without putting on 

 Canada balsam and a coverglass) will shew ex- 

 cellent results after many years. Films that have 

 been unfixed at the time of making, and that may 

 have subsequently become damp, will have their 

 red cells destroyed, but the parasites will still 

 stain. 



The method of wrapping one's slides up in 

 paper (after duly labelling) is in practice the most 

 convenient one, especially if travelling, when not 

 unfrequently boxes of slides suffer much damage. 



To Fix Films 



Until a film has been ' fixed ' it is soluble in 

 water, and will be immediately washed oft' if 

 placed in water or any watery solution of a stain. 

 WJien fixed it is insoluble, and may be treated in 

 almost any way without destruction. Except 

 when using Leishman's combined fixing and stain- 

 ing solution, the film must always be ' fixed.' 



On returning home or to the laboratory, place 

 the films in a glass-stoppered cylindrical jar, 

 about four inches high and one-and-a-half inch 

 diameter, containing absolute alcohol. . When a 

 number of slides are taken, they are placed in 



