CHAPTER XVII 



■ PLASMODROMATA AND SARCODINA 



Preliminary — Animal parasites — Nomenclature — Classification — Protozoa — 

 Classification — Plasmodromata — Sarcodina — Gymnamoebida — Loeschia 

 — Vahlkamfia — Dientamoeba — Craigia — Thecamoebida — Chlamydophrys 

 — References. 



PRELIMINARY. 



In tropical medicine the parasitic causes of disease are extremely 

 important, and it is well to be clear as to the meaning of the term 

 ' parasite.' A parasite is defined to be a living organism, animal 

 or vegetal, which takes up its abode temporarily or permanently on 

 or within other living organisms (called the hosts) for the purpose 

 of obtaining food. Parasites may be divided into animal parasites 

 and vegetal parasites, and it is with the former that we are con- 

 cerned in this chapter. 



ANIMAL PARASITES. 



Animal parasites (zooparasites), in the process of obtaining their 

 food, may cause disease by their mechanical action and chemical 

 products, or by introducing into the host pathogenic micro- 

 organisms. 



As examples of the latter may be mentioned the transmission of 

 the animal organism which causes malaria by certain members of a 

 family of the mosquitoes, or that of the vegetal organism which is 

 the cause of plague by certain fleas. Intestinal worms probably 

 cause many of the symptoms of the disease with which they are 

 associated by the introduction into the body of poisons through 

 their bites, or, according to Sambon and other observers, by their 

 active migrations before attaining maturity and reaching their 

 selective anatomical habitat. 



A well-known example of the irritation caused by the introduction 

 of chemical poisons is the ordinary mosquito-bite already described, 

 while Trichinella spiralis Owen, 1835, produces severe disturbance 

 during its wanderings through the body. 



Mechanically the jigger {Dermatophilus penetrans Guerin, 1838) 

 causes much irritation to the foot, andLo^ loa (Guiyot, 1778) to the 

 eye. 



Animals may be only ' temporary parasites ' — i.e., they may only 

 temporarily afiect the host, as, for example, mosquitoes — or they 

 • may be ' stationary parasites,' such as the malarial organism which 



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