32 CLINICAL BACTERIOLOGY AND H/EMATOLOGY 



The use of new slides and cover-glasses facilitates the task of 

 the bacteriologist to an extent which more than compensates 

 their expense. Old slides and cover-glasses may be used for 

 sections. 



Slides are best cleansed by dropping them one at a time into 

 strong nitric or sulphuric acid, and allowing them to soak for 

 an hour or more. They are then washed in running' water for 

 another hour, soaked in strong ammonia for an hour, and kept 

 in alcohol. As methylated spirit is not so good for this pur- 

 pose, the use of alcohol is rather expensive; but it is not 

 absolutely necessary, and the slides may be stored in a solution 

 of ammonia (about i in 10) until required. When about to be 

 used, they are to be wiped dry with an old linen handkerchief 

 kept specially for the purpose. This handkerchief should be 

 as old as possible, and should have been washed until it has 

 begun to fall to pieces. 



Another and more rapid method is to place the slides in a 

 thin glass or earthenware vessel and moisten them with methy- 

 lated spirit, and then to cover them completely with strong 

 commercial nitric acid, placing the vessel in the open air. In a 

 little while the acid will become very hot and emit copious 

 fumes. When the ebullition has ceased, any fat which may be 

 present will have melted, and will form a pellicle on the sur- 

 face, whilst other' organic materials will have been destroyed. 

 The acid is then to be poured off, taking care to remove the 

 pellicle of grease with it, and a stream of water allowed to fall 

 into the vessel until the acid has been washed away. The slides 

 (and the method is a good one for cover-glasses also) may 

 then be placed in absolute alcohol or methylated spirit, and 

 only require drying to be ready for use. 



Another method which I have recently used and found ex- 

 cellent is to boil them in a 5 per cent, solution of lysol; they 

 may be allowed to remain in this fluid until required, and are 

 then polished with a handkerchief and it may be pointed out 

 that thorough friction is a sine qua non whatever method of 

 cleaning be adopted. Slides and cover-glasses after use may 

 be soaked in the lysol solution, a pot of which should be kept 

 at hand for the purpose; they will be sterilized and partially 

 cleaned in a few hours. 



When no properly cleaned slides are at hand, the following 

 method may be adopted, though it is not so good : dip the end 



