CHAPTER III. 



MICROSCOPICAL EXAMINATION OF BACTERIA IN 

 LIQUIDS, IN CULTIVATIONS ON SOLID MEDIA, 

 AND IN TISSUES. 



Preliminary Remarks. In conducting bac- 

 teriological researches, the importance of absolute 

 cleanliness cannot be too strongly insisted upon. 

 All instruments, glass vessels, slides, and cover 

 glasses should be thoroughly cleansed before 

 use. A wide-mouthed glass jar should always 

 be close at hand, containing refuse alcohol for 

 the reception of rejected slide preparations, or 

 dirty cover-glasses. When required again for 

 use, slides can be easily wiped clean with a soft 

 rag. Cover-glasses require further treatment, for 

 unless they are perfectly clean it is difficult to 

 avoid the presence of air bubbles when mounting 

 specimens. They should be left in strong acid 

 (hydrochloric, sulphuric, or nitric) for some hours; 

 they are then washed, first with water and then 

 with alcohol, and carefully wiped with a soft rag. 

 The same principle applies in the preparation 

 and employments of culture media ; any laxity in 

 the processes of sterilisation, or insufficient atten- 



