PREFACE vii 



they pretend to cover the whole ground of Practical 

 Bacteriology. In three months it is impossible to teach 

 or to learn much. Hence we have attempted to make the 

 Lessons as representative as possible, and to introduce the 

 student to the more important analytical studies and prob- 

 lems. Parts I. and II. are especially arranged to suit the 

 requirements of candidates for one or other Diploma in 

 Public Health. 



We have always described methods which we use our- 

 selves, and in all cases we have given frankly and without 

 reserve what we consider to be the quickest or the best 

 method. Every laboratory has its own ways and means, 

 its "short cuts," and we might almost say its "secrets." 

 We have divulged all our own, not because we flatter our- 

 selves that there are no better methods, but because we have 

 found from practical experience that most methods depend 

 in their execution on some small detail which is frequently 

 withheld from the beginner. These so-called " laboratory 

 tips," which are acquired through experience and practice, 

 are often omitted in descriptions of special methods, 

 because they seem unimportant, or possibly too precious. 

 Methods which require acquaintance with glass-blowing, 

 or which recommend themselves readily enough to old 

 hands but seem unsuited to the inexperienced, have been 

 purposely left out. 



We confess at once that the methods described in these 

 Lessons for the most part are not our own. They have 

 been carried away from the various laboratories in which 



