PREFACE. 



THE science of Bacteriology has, within recent years, become 

 so extensive, that in treating the subject in a book of this size 

 we are necessarily restricted to some special departments, 

 unless the description is to be of a superficial character. 

 Accordingly, as this work is intended primarily for students 

 and practitioners of medicine, only those bacteria which 

 are associated with disease in the human subject have been 

 considered. We have made it a chief endeavour to render 

 the work of practical utility for beginners, and, in the 

 account of the more important methods, have given 

 elementary details which our experience in the practical 

 teaching of the subject has shown to be necessary. 



In the systematic description of the various bacteria, 

 an attempt has been made to bring into prominence 

 the evidence of their having an etiological relationship to 

 the corresponding diseases, to point out the general laws 

 governing their action as producers of disease, and to con- 

 sider the effects in particular instances of various modifying 

 circumstances. Much research on certain subjects is so 

 recent that conclusions on many points must necessarily 



