SPOROZOA 427 



malaria due to infection with PL malaria, the fever recurs at 

 intervals of 72 hours, again at the stage of segmentation in die- 

 asexual cycle of the parasite. Obviously an association of two 

 or more crops of parasites reaching maturity at different times 

 may give rise to a variety of fever curves. 



The diagnosis of malaria is most conclusively established by 

 recognizing the parasites in the blood of the patient. One should 

 examine a fresh drop of blood, unstained, under the microscope, 

 and also thin films of blood stained with some one of the Ro- 

 manowsky stains. The parasites may be very scarce in old cases 

 and especially in those patients who have been treated. 



The mosquitoes which transmit human malaria were first 

 recognized by Ross and have been most thoroughly studied by 

 Grassi. The mosquito is capable of causing malaria only after 

 it has fed upon a person harboring the parasite in his blood. 1 The 

 members of the genus Culex, the most common mosquitoes, do 

 not permit the development of the plasmodia within them, but 

 this occurs, so far as is known, only in certain species of the genus 

 Anopheles, A. maculipennis appears to be the most important 

 species. It is easily recognized by the four small black spots on 

 each wing due to a relative accumulation of pigmented scales in 

 these situations. The members of the genus Anopheles are read- 

 ily distinguishable from Culex by the form and arrangement of 

 their eggs, the form and position of the larvae and by the general 

 form and structure of the adult insect, as well as its posture when 

 at rest. 



The restriction and prevention of malaria is founded upon the 

 knowledge of its nature and its mode of spread. The measures 

 include (i) the destruction of malarial parasites in man by thor- 

 ough treatment of the disease with quinine, (2) destruction of 

 mosquitoes and mosquito larvae and the drainage, oiling or screen- 

 ing of their breeding places, and (3) exclusion of mosquitoes from 

 contact with infected persons and also from contact with healthy 

 persons, by the use of screens. The thorough application of 



1 Fermi and Lumbau: Centrbl. f. Bakt., 1912, Bd. LXV, pp. 105-112. 



