230 DISEASES DUE TO HELMINTHS 



healthy individual, but when in a dysenteric or typhoid intestine 

 their presence is more serious. 



(5) The bacterial infection induced by them. The Trichuris 

 trichiura is harmless in itself but can introduce bacteria into 

 the mucous membrane of the appendix, &c., and set up an 

 inflammatory condition. Helminths are usually covered ex- 

 ternally by bacteria, and their intestines may contain a most 

 extensive microbic flora. 



(6) Their selective action. Ankylostomes are always found in the 

 small intestine. They will pass through the skin, veins, heart, 

 lungs, bronchi, trachea, oesophagus and stomach but will not 

 rest anywhere until they have reached the small intestine. 

 Perhaps there is a special secretion there which thev prefer. 

 Again, trematodes select out their own special mollusc. If 

 trematode embryos are placed in a tank with various molluscs 

 the embryos will be attracted by one particular variety only. 

 They will even prefer the fluid in which their special mollusc 

 has been placed and removed, ignoring all other fluids that are 

 the same in every other respect. 



The condition produced may be the result of : — 



A mechanical erosion of tissue. 



The absorption of food materials ingested. 



Toxagmic poisoning. 



Fibrosis, eosinophilia, and secondary amemia. 



The retention of essential glandular secretion. 



NOMENCLATURE. 



There has been and is still much confusion in the naming of 

 parasites. A close study must be made of the literature of any sup- 

 posed new species before names are applied. 



As a guide to those who may require them, a set of rules has been 

 drawn up to regulate the giving of names, and are known as : — 



The International Rules of Xonicncldturc. 

 (i) The Language Rule. 



The scientific names of animals must be Latin or latinized, or 



treated as such. 



The generic name has a capital, the specific name a small letter. 



The generic name must be one word and used in the singular. 



The sub-genus, when one is present, can be inserted in 



brackets, with a capital letter between the genus and the specific 



name. 



The family name ends in " Idx," the sub-family in " in^e." 



The author of a scientific name is the one who first publishes 



