. Essentials of biology presented in problems. Biology. 196 THE PROTOZOA tiny organisms from the water as it passes over the gills. The whale, the largest of all mammals, strains protozoans and other small animals and plants out of the water by means of hanging plates of whalebone, the slender filaments of which form a sieve from the top to the bottom of the mouth. Relation of Protozoa to Disease. — The study of the life history and habits of the Protozoa has resulted in the finding of many parasitic forms, and the consequent explanation of some kinds of disease. One parasitic protozoan like a
. Essentials of biology presented in problems. Biology. 196 THE PROTOZOA tiny organisms from the water as it passes over the gills. The whale, the largest of all mammals, strains protozoans and other small animals and plants out of the water by means of hanging plates of whalebone, the slender filaments of which form a sieve from the top to the bottom of the mouth. Relation of Protozoa to Disease. — The study of the life history and habits of the Protozoa has resulted in the finding of many parasitic forms, and the consequent explanation of some kinds of disease. One parasitic protozoan like an amoeba is called Plasmodium malarice. It causes the disease known as malaria. Part of its life is passed with- in the body of a mosquito (the anopheles), into the stomach of which it passes when the mosquito sucks the blood from a person having malaria. Within the body of the mosquito a com- plicated part of the life history takes place, which results in a stage of the parasite establish- ing itself within the glands which secrete the saliva of the mos- quito. When the mosquito pierces its human prey a second time, some of the parasites are introduced into the blood along with the saliva. These para- sites enter the corpuscles of the blood, increase in size, and then form spores. The rapid process of spore formation results in the chill of malaria. Later, when the spores almost fill the blood corpuscle, it bursts, and the parasites enter the fluid portion of the blood. There they release a poison which causes the fever. The spores may again enter the blood corpuscles and in forty-eight or seventy-two hours repeat the process thus described. Yellow fever is undoubtedly conveyed by another species of mosquito, and is probably due to the presence of a protozoan similar to that of malaria in the blood. That these diseases may be stamped out by the destruction of the mosquitoes, by preventing their breed-. Blood corpuscles of a patient with malarial fever. Two corpuscles con- ta
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
