VI PREFACE. 



be of a tentative character. We have, therefore, 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 import- 

 ance 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 preparations from which Figs. 102-107 

 have been executed. 



As we are convinced that to any one engaged in practical 

 study, photographs and photomicrographs supply the most 

 useful and exact information, we have used these almost 

 exclusively in illustration of the systematic description. 

 These have been executed in the Pathological Laboratory 

 of the University of Edinburgh by Mr. Richard Muir. 

 The line drawings were prepared for us by Mr. Alfred 

 Robinson, of the University Museum, Oxford. 



To the volume is appended a short bibliography, which, 

 while having no pretension to completeness, will, we hope, 

 be of use in putting those who desire further information 

 on the track of the principal papers which have been pub- 

 lished on each of the subjects considered. 



June 1897. 



