PARASITOLOGY. 
INTRODUCTORY. 
The study of parasites is called PARASITOLOGY. 
The study of worms is called HELMINTHOLOGY. 
The condition of an animal infested with parasites 
is called PARASITISM. 
Organisms that live upon different hosts are called 
FACULTATIVE PARASITES. 
Organisms that pass their entire life upon a single 
host cause CONSTANT PARASITISM. 
Parasites that visit their host for nourishment 
only, as is the habit of blood-sucking flies, are 
iNTERMITTENT PARASITES. 
Parasites that pass part of their life external to 
their host, as species of the bot-fly family, are TRAN- 
GITORY PARASITES. 
Parasites that can live only upon one species of 
animals are called OBLIGATORY PARASITES. 
Animal parasites are separated into two divisions, 
viz.: Ectozoa, or external parasites, and Entozoa, 
or internal parasites. 
Ectozoa (ektos—without, zoa—animal) are those 
parasites that live outside the body. 
Entozoa (entos—within, zoa—animal) are those 
parasites that live within the body. 
A Parasite is an organism, animal or vegetable, 
that lives upon another organism, animal or veg- 
etable. 
Parasites are placed in three bra@ches, viz.: Arth- 
ropoda, Vermes, and Protozoa. 
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