Protozoon

pro-to-zoon, plura! protozoa, a minute animal. The protozoa are simple in structure and difficult to distinguish from the lowest plants or bacteria. Like bacteria, they multiply usually by the division of the parent into new animals, or by the production of a sac full of spores. Many diseases of animals and of the human race are now attributed with reasonable certainty to colonies of protozoa living on the red corpuscles of the blood. Such diseases are infectious. Malaria, Texas cattle fever, and the tsetse fly fever are of this sort. Smallpox, yellow fever, and other epidemics are due to microbes parasitic in the blood. See Bacteria; Disease; Yellow Fever