8 SOME FACTS ABOUT MALARIA. 
the mosquito’s stomach. It passes through the stomach wall and 
finally affixes itself to its outer surface. 
Here it grows very considerably and, after a week under favorable 
conditions, produces a large number of spores. 
These spores, thus entering the general body cavity of the mosquito, 
find their way into the salivary glands. These glands secrete the 
irritating fluid injected under the human skin when the mosquito 
begins to feed. 
Thus, when one of these mosquitoes, which has fed upon a malarial 
patient containing the sexual forms of the parasites, bites, after a 
week, another person, it injects these spores together with its saliva 
under his skin and generally into his blood. 
These spores now cause or may cause infection or reinfection in 
this second person. 
Thus the parasites of malaria pass from men to certain mosquitoes 
and back from these mosquitoes to men. 
Malarial fever is then an infectious disease, which is carried from 
the sick to the healthy by anopheline mosquitoes, and only in this 
way can it be contracted. 
It has always been known that malaria is most prevalent in the 
vicinity of marshes, and it was formerly supposed that the air or 
exhalations from these marshes produced the disease. Parasites of 
malaria have not been found in the water or air of marshes, nor in 
decaying vegetation, nor in the soil, although they have been dili- 
gently searched for. Attempts to produce infection by these agencies 
have always failed. The mosquitoes which carry these parasites, 
however, breed in marshes or in marshy pools and streams. 
Issuing from these breeding places, they enter nearby houses and 
feed upon the inmates, mostly at night, biting first one person and 
then others, and living for weeks or months. 
If an infected person happens to be present in any of these houses, 
the anopheline mosquitoes biting him will also become infected, and 
the disease is likely, ultimately, to be carried by these mosquitoes to 
others and to neighboring houses. 
Thus a whole neighborhood soon becomes infected and the locality 
is called malarious. In such localities it is easy to find the parasites 
of malaria in the proper mosquitoes. Sometimes 25 per cent or more 
of them are found to be infected. 
In malarious localities the anopheline mosquitoes bite the healthy 
new-born children and infect many of them. 
Such children if not thoroughly treated may remain infected for 
years. They may become anemic and possess enlarged spleens, and 
of course may spread the infection to others. 
In malarious localities almost every child has been found to con- 
tain the parasites of malaria or to possess an enlarged spleen. 
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