446 SPECIFIC MICRO-ORGANISMS^ 



or more crops of parasites reaching maturity at diffetent 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 Romanowsky 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. ^ 

 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 in Europe and A. quadrimaculatus 

 in America appear to be the most important species. They are 

 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 readily 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 larvje 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 these measures has demonstrated the possibility of effectively 

 controlUng this disease even in the tropics. 



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



