PREFACE TO THE SECOND EDITION. 



Although there has been no lack of works on bacteriology, 

 it seemed to the writer that there was stiU a field open for one 

 which sought to give the portions essential to medical science in 

 a concise manner. It is gratifying, therefore, that the first 

 edition of this little book should have been exhausted so soon. 



Whether wisely or not, it is a fact that many medical schools 

 require their students to absorb an amount of knowledge that 

 taxes the brain to the utmost. While such conditions remain, 

 the need is urgent for presenting what is taught in the accessory 

 branches in as condensed a form as is consistent vnth a clear 

 understanding of their great fundamental principles. It is 

 mastery of such principles, after all, which is the object of a 

 course in bacteriology, for they are essential to a correct under- 

 standing of most of the other branches. After that has been 

 accomplished (including the applications of bacteriology to 

 diagnosis), it must be admitted that other branches deserve a 

 larger amount of the student's time. This may be said without 

 meaning to minimize the importance of bacteriology in the train- 

 ing of a physician. In the opinion of the writer it is neither 

 possible nor desirable that every graduate should be a trained 

 bacteriologist. However, no instructor can hope to bring the 

 principles above mentioned home to his classes except by labo- 

 ratory work. Very little attempt has been made to outline the 

 program of a laboratory course, as that will always need to be 

 planned according to the circumstances under which it is given. 



The purpose of this book is to give in the smallest possible 

 space the facts which a physician must know, with some of those 



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