PRACTICAL BACTERIOLOGY. 



(Heidelberg), which have an arrangement for regu- 

 lating simultaneously the supplies of gas and air. 



24. A micro-burner for warming the incubator. 

 Koch's safety burners are the best for this purpose, 

 but they are unreasonably dear. See page 89. 



25. An incubator. However, unless great uniform- 

 ity of temperature is necessary, this can be replaced by 

 the very simple apparatus described on p. 88. 



26. A steam steriliser (Pig. 4). 



27. A hot air steriliser (Fig. 3). 



28. A balance. Should a delicate chemical balance 

 be unobtainable, an ordinary pair of scales for weigh- 

 ing gelatine, peptone, staining reagents, etc., will 

 answer the purpose. Great exactness is only essential 



. in a few cases ; for example, in the preparation of nor- 

 mal solutions, such as the caustic soda solution used for 

 staining flagella. In such cases, however, the reagents 

 can always be obtained ready-made from a reliable 

 chemical manufacturer, or they may be ordered at a 

 chemist's or from a chemical laboratory. The need for 

 a delicate balance so seldom arises that it is hardly 

 worth while to procure one. 



29. A filter stand. 



30. Filter paper, somewhat thick for filtering gela- 

 tine and agar-agar, and a thinner kind, not very per- 

 meable, for filtering the staining solutions. Folded 

 filter papers are used for gelatine : these can be ob- 

 tained ready-made. For staining reagents it is best 



