REAGENTS USED IN BACTERIOLOGICAL RESEARCH 29 



Soyka's plates are similar to Petri's capsules, but differ 

 from them in having eight to ten depressions ground in the 

 lower plate, which resemble the ' wells ' in hollowed slides. 



In addition to the above, all articles employed in 

 microscopic investigation are required. The slides used 

 for examining micro-organisms in the ' hanging drop ' have 

 a well ground in the centre (fig. 17) . This is covered with 

 a cover- glass the lower surface of which has been prepared 

 with the micro-organism. 



Crates of galvanised wire are used for holding glass 

 utensils, especially test-tubes, while being sterilised (fig. 18). 



Reagents, It is scarcely possible to give a complete list 



Well 



FIG. 17. HOLLOW SLIDE. 



FIG. 18. WIRE CIIATE. 



of all the reagents used in bacteriological research, since 

 recourse must be had as much as possible, according to the 

 nature of the particular investigation, to the province of 

 the auxiliary sciences, including, of course, chemistry. 

 Speaking generally, the reagents used are acids, salts, disin- 

 fecting fluids, various oils, colouring matters, and other drugs. 



Of acids, those most used are sulphuric, nitric, chromic, 

 acetic, and oxalic, and less frequently also dilute osmic acid. 



Of alkalis and salts, solutions of caustic potash and 

 soda and lime water are employed, also the bicarbonates of 

 potassium and sodium, sodium chloride, potassium iodide, 

 iron perchloride, ammonium carbonate, and potash-ammonia 

 alum. 



