Any of several minute protozoans of the genus Plasmodium (syn. Hæmatozoön) which in their adult condition live in the tissues of mosquitoes of the genus Anopheles (which see) and when transferred to the blood of man, by the bite of the mosquito, produce malaria. The young parasites, or sporozoites, enter the red blood corpuscles, growing at their expense, undergoing sporulation, and finally destroying the corpuscles, thus liberating in the blood plasma an immense number of small spores called merozoites. An indefinite but not ultimated number of such generations may follow, but if meanwhile the host is bitten by a mosquito, the parasites develop into gametes in the stomach of the insect. These conjugate, the zygote thus produced divides, forming spores, and eventually sporozoites, which, penetrating to the salivary glands of the mosquito, may be introduced into a new host. The attacks of the disease coincide with the dissolution of the corpuscles and liberation of the spores and products of growth of the parasites into the blood plasma. Several species of the parasite are distinguished, as P. vivax, producing tertian malaria; P. malariæ, quartan malaria; and P. (subgenus Laverania) falciferum, the malarial fever of summer and autumn common in the tropics.
© Webster 1913