PARASITES.
—These are living plants or animals that live temporarily or continually in the bodies of other plants or animals and draw their nourishment from their host. It is doubtful if there is a single farm animal that does not harbor parasites at nearly all times during its life. There may be many of these in the same individual at the same time. Parasites may be harmful or not, as the case may be. Parasites may be divided into two classes—plant parasites and animal parasites. The bacteria and molds are the most important among the former, whereas in the latter certain minute protozoa, certain forms of insects and certain worms are the most commonly met. Such diseases as staggers, tuberculosis, and typhoid fever are the result of bacterial diseases, while Texas fever is an example of the protozoa class; and then the insects and worms are types with which we are all acquainted. When a disease is caused by either, discussion will be found under the name of that disease.