PREFACE TO THE FOURTH EDITION 



IN preparing this book I had in my mind the requirements of 

 the practitioner who has had but little or no training in bac- 

 teriology and haematology, and who wishes to know what help 

 may be afforded him by these two sciences in his everyday 

 practice. I have tried to give clear and succinct information of 

 the conditions in which these new branches of pathological 

 work may help him, exact information how to proceed, and 

 advice as to the circumstances in which it is necessary to have 

 recourse to expert assistance. The facts that three editions of 

 this book have been exhausted since its appearance in 1902, 

 and that I have received numerous and kind letters concerning 

 it from practitioners in all parts of the world, lead me to think 

 that it has proved useful to the class of readers to whom it was 

 addressed. I have therefore made comparatively slight altera- 

 tions in this edition. It seemed advisable to add an account of 

 a simplified method for the Wassermann reaction, which in my 

 hands has yielded very good results; not so much because I 

 think it should be carried out by anyone who is not an expert, 

 but because it serves as an introduction to a matter of profound 

 importance to every medical man the interpretation of the 

 results of the test. This I have dealt with at some length. 

 Apart from this the alterations in this edition are mainly in 

 matters of detail. 



I have, as before, to express my thanks to Professor Leith 

 of Birmingham and to Dr. Whitfield for many kind sugges- 

 tions; to the latter for his photographs reproduced on Plates 

 IV. and VI., to Dr. Gompertz for Figs. 28, 31, and 42, and to 

 Dr. H. B. Day for Figs. 16, 17, and 18; and to Messrs. Baird 

 and Tatlock, Swift and Sons, Leitz, Zeiss, Hawksley, Down 

 and Hearson for the loan of blocks of apparatus. 



July, 1912. 



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