PREFACE TO THE FOURTH EDITION. IX 



have already appeared in my Reports to the Board of 

 Agriculture and iu other publications. 



One hundred and thirty-three woodcuts and photographs 

 have been added in the text, and I have reverted to the plan 

 which T adopted in the second edition, of having many of 

 them printed in. colours. 



I take this opportunity of thanking Professor Frankel for 

 kindly permitting me to reproduce some of the photographs 

 in his excellent Atlas. 



I am particularly indebted to Professor Hamilton for 

 the use of cliches of figures in his classical treatise on 

 Pathology, and to the New Sydenham Society for several 

 from the' English translation of Professor Flugge's well- 

 known work on micro-organisms. 



To my Demonstrator, Dr. George Newman, D.P.H., I am 

 indebted for much assistance in correcting the proof-sheets, 

 and for the preparation of an index. 



EDGAR M. CROOKSHANK. 



Saint Hill, East Geinstbad, Sussex, 

 August 1st, 1896. 



P.S, — Since this work was finally passed for press the con- 

 clusions of the Royal Vaccination Commissioners have been 

 published. I have at the last moment added extracts in the 

 form of a supplementary Appendix. E. M. 0. 



September IStJi, 1896. 



