METHODS OF STUDYING BACTERIA 23 



CHAPTER IV 



METHODS OF STUDYING BACTERIA; AND THEIR 

 MORPHOLOGY AND LIFE-HISTORY 



PERHAPS the most important instrument in the bacteriologist's 



outfit is a good Compound Microscope of sufficient power, i.e. 



capable of magnifying by about one thousand diameters. For 



a detailed description of such a micro- 



scope, reference should be made to 



books on optics and to the illus- 



trated catalogues of the instrument 



makers, and it is sufficient for our 



present purpose to refer the reader 



to the accompanying illustration 



(see Fig. 1). The usual outfit of 



microscopical accessories, such as 



slides, specially thin or " No. 1 " 



cover-slips, etc., are of course also 



required. 



With regard to the various Stains 

 or Dyes and other reagents em- 

 ployed to differentiate and make 

 micro-organisms more easily visible, 

 it is sufficient here to say that the 

 bacterial protoplasm as a rule stains 

 most readily with the basic aniline 

 dyes. Protozoal parasites are usually 

 demonstrated by rather more com- 

 plex methods of staining, and 

 for the technical details refer- 

 ence should be made to the 

 specialtext-books enumerated 

 at the end of this volume. 



T , j ,, 



In order to study thor- Fm 

 oughly any given organism, Microscope, 



it is usually desirable to be 



, , , . J . ., . .. 



able to isolate it from other 



contaminating microbes, and 

 therefore one of the first problems we have to face is how 

 these contaminating microbes are to be excluded from our 

 apparatus, and this leads us to a consideration of the im- 

 portant subject of Sterilisation, i.e. the means by which we 

 can destroy any organisms already present, and then exclude all 

 others except the special variety we wish to study. We must 



Model Bacteriological 

 fitted with eye-piece, 

 Abbe condenser and iris diaphragm, 

 triple nose-piece, and three obiec- 

 tives. 



