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 
