Let us briefly consider what the farmer or the resident of a small 

 village must do to bring about protection. 



MALARIA. 



The old idea that malaria is caused b}- breathing the miasma of 

 swamps has been exploded. Malaria is contracted onlj^ through the 

 bites of mosquitoes of the genus Anopheles. The cause of human 

 malaria is the growth and development within the red blood cells of a 

 very minute parasitic organism belonging to the lowest group of the 

 animal kingdom— the group Protozoa, or one-celled animals, which 

 includes those minute creatures known as Amoebas and others, and 

 which live in the water or in damp sands or moss, or inside the bodies 

 of other animals as parasites. This parasite reproduces in the body 

 by subdividing, eventually bursting the red blood cells and entering 

 the blood serum as a mass of spores. Broadly speaking, when the 

 blood of a human being is sucked into the stomach of a mosquito of 

 the genus Anopheles the malarial parasite undergoes a sexual develop- 

 ment and gives birth tq a large number of minute, spindle-shaped 

 cells, known as blasts, which enter the salivary glands of the insect and 

 are ejected with the poison into the system of the next person bitten 

 by the mosquito. If this person happens to be nonmalarious the 

 malaria has thus entered his system and malarial symptoms result. 



So far as present knowledge goes, this is the only way in which 

 people become malarious. In order to avoid this result it is necessary 

 to avoid the bites of malarial mosquitoes, and it therefore becomes 

 important to know the difi'erences between the malarial and the more 

 harmless mosquitoes, and the conditions under which the malarial 

 forms breed. 



Malaria-bearing mosquitoes. — There are very many mosquitoes which 

 have not yet been proven to carry any disease. In fact, the majority 

 of mosquitoes are supposed to be harmless except for the irritation 

 caused b}^ their punctures. The commonest of all forms belong to the 

 genus Culex. These include the mosquitoes most commonly breeding 

 in rain-water barrels and chance transient pools. Fig. 1 shows the 

 diflerence between a harmless mosquijio of the genus Culex and the 

 malarious mosquito of the genus Anopheles. It will be noticed that 

 Culex has clear wings, while Anopheles has wings which are more or 

 less spotted. It will be noticed further that while the palpi (which 

 are the projections either side of the beak) are ver}^ short in Culex, 

 they are long — nearly as long as the beak — in Anopheles. Further, 

 it has been observed that when Culex is resting upon a wall it appears 

 more or less humpbacked, that is to say, the head and the beak are 

 not in the same plane with the body and wings, but project at an angle 

 toward the surface of the wall, the body and wings being parallel with 

 the wall. With Anopheles, however, the head and beak are in prac- 



