CHAPTEE II. 



BACTERIOLOGICAL APPARATUS— PREPARATION OF 



NUTRIENT MEDIA, ETC. 



The apparatus used in bacteriological research— The microscope— Hot- 

 air and steam sterilisers— High pressure steam sterilisers— Inter- 

 mittent steriUsation— Sterilisation by means of chemical agents and 

 filtration— Freezing and other microtomes— Incubators, warm and 

 cool — Centrifugal machines — Other bacteriological apparatus — 

 Nutrient media and their preparation. 



The Microscope. — This instrument is perhaps the most 

 important piece of apparatus used by the bacteriologist. 

 Owing to the bacteria being the smallest and simplest living 

 forms with which we are at present acquainted, it will be 

 seen that it is of the greatest importance to be provided 

 with a first-class microscope. Microscopes especially de- 

 signed for bacteriological w;ork are manufactured by the 

 following well-known firms : Messrs. Zeiss, Leitz, Powell 

 and Lealand, Baker, Beck, Watson and others. All the 

 instruments and lenses made by these firms are of the 

 highest class, both in performance and workmanship. Fig. 

 2 shows Messrs. Watson and Son's Edinburgh Student's 

 Microscope, completely fitted with all the accessories neces- 

 sary for bacteriological work. We have found this instru- 

 ment to bo very suitable for bacteriological research, and 

 thoroughly satisfactory in practice. 



A microscope suited for bacteriological work should 

 satisfy the following requirements : The stand should be 

 absolutely rigid, and the fine adjustment should be both 

 sensitive and precise in its action. The instrument must 

 be fitted with an Abb6 sub-stage condenser and iris dia- 



