INTRODUCTION 7 



But none of these reputed transformations of bacteria 

 can be accepted as proved until the same results are 

 obtained with cultures derived from a single cell. 



Minchin in a presidential address to the Quekett 

 Microscopical Club pointed out that syngamy (sexual 

 reproduction, e.g. conjugation) is of the greatest import- 

 ance in preserving differentiation of species, and that 

 without it a species will tend to break up into races. 

 It therefore follows that there are no true species among 

 organisms of the bacterial grade, if it be true, as is usually 

 held, that syngamy does not occur amongst them, and the 

 so-called species of bacteria are to be regarded as mere 

 races or strains capable of modification in any direction. 



Bacteriology has made vast strides during the last 

 two or three decades, but much still remains to be done. 

 The causative organisms of several infective diseases are 

 still unknown, the perplexing problems of susceptibility 

 and immunity are not yet fully elucidated, and the cure, 

 control and prevention of many infective diseases are by 

 no means fully accomplished. 



The literature of Bacteriology has now become somewhat exten- 

 sive. In the following pages references to original papers have 

 been freely introduced, many of which contain a more or less full 

 bibliography on the subject referred to, so that further informa- 

 tion may be obtained if required. Kolle and Wassermann's 

 Handbuch der Pathogenen Mikroorganismen, ed. ii., is the most 

 encyclopaedic work on pathological bacteriology yet published. 



Valuable summaries of current researches will be found in 

 Abstracts of Bacteriology, Bulletin de Vlnstitut. Pasteur and Cen- 

 tralblatt fur Bakteriologie. 



