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 
