CHAPTER XII. 



THE PREPARATION, STAINING, AND MICROSCOPICAL 

 EXAMINATION OF BACTERIA. 



As the purpose of this book is to give, outside of 

 special methods devised for purposes of diagnosis and 

 the development of curative serums, only such descrip- 

 tions of technique as are necessary to students in their 

 laboratory courses, or to physicians in the very simple 

 examinations which they will be able to carry on in 

 their private offices, readers are referred to works 

 such as Sternberg's or Abbott's for fuller descriptions 

 of the apparatus and technique used in bacteriological 

 research. 



Since bacteria are present to a greater or less extent 

 in the air, earth, and water around us, on our bodies, 

 clothes, and all surrounding objects, it follows that 

 when we begin to examine substances for bacteria the 

 first requisite is that all the materials we use must be 

 free and kept free from bacteria, both living and dead, 

 otherwise we cannot tell whether those we detect are 

 in the substances examined or only in the materials we 

 have used in the investigation. 



Additional care has to be taken when we study in- 

 fection in the living body, for in the skin and mucous 

 membranes there are not only abundant bacteria but 

 varieties similar to those which produce disease, so that 

 if we do not use the greatest precautions we will con- 

 taminate our material with these bacteria and get utterly 



