CHAPTER V. 

 ANIMAL PARASITES. 



Man is host for numerous animal parasites both 

 large and small. A parasite, we have seen, is ''an 

 organism which lives upon another organism called the 

 host." Parasites may live permanently upon their 

 hosts, or be only temporary inhabitants. They may 

 have their habitat upon the exterior of our body, when 

 they are called ecto- parasites; or within it {endo-para- 

 sites). All human ecto-parasites are either mites 

 (arachnida), or true insects; all endo-parasites belong 

 to the protozoa, trematoda, cestoda, or nematoda. 



By temporary parasite is implied an organism which 

 seeks the human body for a single meal only, and passes 

 for the next to a new host. To this class belongs 

 mosquitoes, bed-bugs, ticks, etc. By permanent para- 

 site is understood an organism which, when it finds 

 lodgment upon or within the body, remains there 

 until dislodged either by accident, through the instru- 

 mentality of drugs, or because the host is no longer a 

 suitable pabulum either for further development or 

 for a continued existence. Death of the host, of course, 

 terminates the status, parasitism. Most human endo- 



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