ANIMAL PARASITES 



287 



hosts,' but at times they are found in unusual hosts — for example, 

 Echinorhynchus gigas (Goeze, 1782), which is usually found in pigs, 

 may infect man. Such a parasite is called a ' chance parasite,' 

 while objects mistaken for parasites are known as ' pseudo- 

 parasites.' 



The above are examples of simple parasitism; but there are para- 

 sites which are parasitic upon other parasites — a condition called 

 ' hyperparasitism.' These hyperparasites may be secondary, 

 tertiary, or quaternary, and their importance in disease has been 

 emphasized by Sambon, who has shown that it may be one of the 

 causes of the disappearance of malaria from a district, for the 

 black spores found by Ross in mosquitoes infected with malaria are 

 now known to be hyperparasites of the genus Nosema. 



For further remarks see the article on Metazoan Parasites. 



Nomenclature. — Medical men in the tropics are at present almost daily 

 discovering new, or what are thought to be new, parasites, and are generally 

 desirous of giving them definite names, but before doing so it behoves the 

 discoverer to know and obey the international code laid down by zoologists, 

 for which purpose they should study Stiles's pamphlet in the bulletins of the 

 United States Public Health and Marine Hospitals Service. 



Four rules may be mentioned here : — 



1. Language Rule. — The name given to the parasite must be in Latin, and 

 not in any vernacular. 



2. Rule of Priority. — The valid name for a genus or species is the oldest 

 V available name. Therefore, in describing a species or genus, give not merely 



the name of the authority who invented the term, but the date also. 



3. Rule of Homonyms. — When two distinct genera or species of animals 

 receive the same name, that applied earliest alone must stand. 



4. Rule of Appropriateness. — ^No name is allowed to be changed simply 

 because it is inappropriate. 



With regard to disease there is no fixed rule, but we feel sure that if medical 

 men would attempt to evolve a fixed method of nomenclature, much confusion 

 would be avoided. 



When an animal parasite causes a series of symptoms in a man or an 

 animal, it is usual to name the affection by that of the animal causing the 

 disease, together with the suffix ' iasis.' Thus, Loeschia histolytica (Schaudinn, 

 1903) causes loeschial dysentery and liver abscess, etc., which may be 

 classed together under the term ' Loeschiasis ' ; or Paragonimus ringeri 

 (Cobbold, 1890) causes a varied number of symptoms, which can all be 

 classed together as' Paragonimiasis.' 



The drawback to this nomenclature is that, parasites being very often 

 changed from genus to genus, such terms are not permanent. For instance, 

 the same pathological condition may be indicated by various authorities 

 with the terms ' Amoebiasis,' ' Entamoebiasis,' ' Loeschiasis.' We therefore 

 prefer, wherever possible, to use common names for diseases — e.g., ' Kala- 

 azar.* 



Classification. — -The animals which cause and convey the diseases 

 of man may be classified into the following subkingdoms: Sub- 

 kingdom I., Protozoa; Subkingdom IL, Metazoa. 



