File:Handbook of medical entomology (1915) (14779284064).jpg

Identifier: handbookofmedic00rile (find matches)
Title: Handbook of medical entomology
Year: 1915 (1910s)
Authors: Riley, William Albert, 1876- Johannsen, Oskar Augustus, 1870-1961 Metcalf Collection (North Carolina State University). NCRS
Subjects: Insect pests Insects as carriers of disease Medical parasitology
Publisher: Ithaca, N.Y., The Comstock publishing company
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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ria but the particular typeof disease. Laveran traced out the life cycle of the malarial parasite as itoccurs in man. The details as we now know them and as they areillustrated by the accompanying figure 125, are as follows: The infecting organism or sporozoite, is introduced into the cir-culation, penetrates a red blood corpuscle, and forms the amoeboidschizont. This lives at the expense of the corpuscle and as it developsthere are deposited in its body scattered black or reddish blackparticles. These are generally called melanin granules, but aremuch better referred to as haemozoin, as they are not related to igo Arthropods as Hosts of Pathogenic Protozoa melanin. The hsemozoin is the most conspicuous part of the para-site, a feature of advantage in diagnosing from unstained prepara-tions. As the schizont matures, its nucleus breaks up into a nimiber ofdaughter nuclei, each with a rounded mass of protoplasm about it,and finally the corpuscles are broken down and these rounded bodies
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125. Life cycle of the malaria parasite. Adapted from Leuckarts chart,by Miss Anna Stryke. are liberated in the plasma as merozoites. These merozoites infectnew cor;Duscles and thus the asexual cycle is continued. The malarialparoxysm is coincident with sporulation. As early as Laverans time it was known that under conditionsnot yet determined there are to be found in the blood of malariouspatients another phase of the parasite, differing in form accordingto the type of the disease. In the pernicious type these appear aslarge, crescent-shaped organisms which have commonly been calledcrescents. We now know that these are sexual forms. Mosquitoes and Malaria 191 When the parasite became known there immediately arose specu-lations as to the way in which it was transferred from man to man.It was thought by some that in nature it occurred as a free-livingamoeba, and that it gained access to man through being taken upwith impure water. However, niunerous attempts to infect healthypersons by

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