vi PREFACE 



to the student trained in chemistry and biology, and it 

 has been thought best to exhibit these, to the smallest 

 detail, by means of illustrations — a feature not sufficiently 

 considered in other guides. 



The formulae for stains and the methods of staining 

 have not been collected in one chapter, as is usually the 

 practice, because this tends to confuse the student. 

 They are described during the progress of the course, as 

 occasion offers to put them to practical use. 



Culture-description charts have not been included in 

 this volume. A beginner naturally makes incomplete 

 descriptions and many alterations, and thus defaces the 

 book and impairs its future utility. A sufficient number 

 of loose charts perforated for binding should be furnished 

 to the student at a nominal figure. 



A point of inestimable importance is how best to 

 stimulate the student to consult textbooks and special 

 monographs, and other references, as often and as freely 

 as possible. This guide has been written with the aim 

 of not only not interfering in any manner with the reading, 

 through including such points and characteristics as might 

 make a textbook superfluous in the judgment of the 

 inexperienced, but also of making it necessary for the 

 student to read the best textbooks with freedom and 

 understanding. Cultural and morphological features are 

 left entirely to the actual observation of the student, sup- 

 plemented by instruction and the reading of textbooks. 



The course, as outlined, is identical with the medical 

 course given at the University of Chicago, with a few 

 additional chapters which may be used during courses 

 for non-medical students. A chapter containing a fairly 

 complete hst of formulse for culture media employed in 



