PREFACE TO THE FIRST EDITION. 



THE science of Bacteriology has, within recent years, be- 

 come 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. Ac- 

 cordingly, as this work is intended primarily for students and 

 practitioners of medicine, only those bacteria which are asso- 

 ciated 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 consider the effects in particular 

 instances of various modifying circumstances. Much research 

 on certain subjects is so recent that conclusions on many points 

 must necessarily be of a tentative character. We have, there- 

 fore, in our statement of results aimed at drawing a distinction 

 between what is proved and what is only probable. 



In an Appendix we have treated of four diseases ; in two of 

 these the causal organism is not a bacterium, whilst in the 

 other two its nature is not yet determined. These diseases 

 have been included on account of their own importance and 

 that of the pathological processes which they illustrate. 



Our best thanks are due to Professor Greenfield for his kind 

 advice in connection with certain parts of the work. We have 

 also great pleasure in acknowledging our indebtedness to Dr. 

 Patrick Manson, who kindly lent us the negatives or prepara- 

 tions from which Figs. 143-148 have been executed. 



