PREFACE TO THE THIRD EDITION 



In the present edition we have to add many new 

 blood parasites. We have thought it best to describe 

 most fully those which are of pathogenic importance, 

 and which cause well-known diseases either in man or 

 animals, so that in the present edition the pathogenic 

 Trypanosomes, Haemamoebidae and Spirochaetes are 

 described more at length that hitherto. A knowledge 

 of ticks has become increasingly important, and the 

 chapters dealing with them have been rewritten and 

 much extended. In order to make room for this new 

 matter we have omitted other matter of less import- 

 ance, e.g., in our consideration of mosquitoes we have 

 found it impossible, and indeed unnecessary, to consider 

 them as a whole, but have endeavoured to describe 

 concisely the Anophelinae only. We have also thought 

 it best to omit the chapter dealing with Filaria. We 

 include, on the other hand, short descriptions of yellow 

 fever and a new unclassified parasite of man occurring 

 in Panama, namely, Histoplasma capsulata. 



February, 1908 



