8 TROPICAL MEDICINE AND HYGIENE 



reports becomes accessible and is closely studied. Some 

 of the old descriptions are vague, and authorities differ 

 as to what the exact animal was to which the generic 

 or specific name was originally given. 



Our present duty is clear : to avoid making use of 

 names, even of provisional names, on any new discovery, 

 without a close study of the names already given and of 

 the literature of the subject. Even as regards the spelling 

 of many of these names there are variations. The names 

 used in this work are in the main those in common use. 



Classification of Human Parasites. If the only worms 

 to be considered were those infesting man, a very simple 

 classification of helminths could be adopted; but, as it is, 

 if human helminthology is not to be in opposition to 

 ordinary zoology, the zoological classification has to be 

 used, though as regards man many genera are not repre- 

 sented and others are only represented by a single species. 

 Closely related though non-parasitic groups may require 

 brief mention. 



Helminths are worms parasitic in man or other animals, 

 at some stages of their existence. The diseases or lesions 

 produced are sometimes grouped together under the head- 

 ing Helminthiasis. The helminths found in man belong 

 to many groups and are subject to the zoological methods 

 of classification into Platyhelminths flukes and tape- 

 worms and Nematohelminths round-worms and each 

 of these divisions is further subdivided. The diseases 

 caused are by some similarly divided according to the 

 group of parasites, or even by others according to species. 

 Some of the terms, such as Filariasis and Ankylostomiasis, 

 are in common use and are, therefore, adopted in this 

 book. 



