MOSQUITOES AND MALARIA 23d 



species of parasitic worms occurring in man. It is an 

 established fact that both eggs and germs are dislodged 

 as the insect walks over cooking and drinking utensils, 

 food and the human body, and it may indeed be true, 

 as many students of the subject believe, that disease is 

 spread over wide areas by this process. " Swatting the 

 fly" is a wise preventive measure, and the additional 

 precaution of screening manure piles and other breeding 

 places of this species is the ounce of prevention that 

 may remove the need for the pound of cure. 



Mosquitoes and Malaria. — The second method 

 whereby disease-producing organisms are transmitted 

 from one individual to another is complicated by the 

 fact that the insect concerned is itself parasitized by the 

 microbe. In other words, the insect acts as a so-called 

 secondary host in which the parasitic organism under- 

 goes certain stages before it is suited to a life in the 

 human body. The malarial parasite is an example of 

 this where certain species of mosquitoes are the dis- 

 tributing agents. 



The parasite responsible for the malarial disease is 

 a very minute unicellular animal, which upon being in- 

 troduced by the bite of a mosquito into the blood stream 

 of man attacks the red blood corpuscle, enters it, con- 

 sumes its substance and then divides into a large number 

 of smaller cells. These escape into the blood, attack new 

 corpuscles and repeat the process. In a few dayS millions 

 of these parasites may be present in the blood, and their 

 destruction of the corpuscles is responsible for the pale- 

 ness of the skin characterizing this disease. With the 

 rupture of the blood cell, and the escape of the impris- 

 oned parasites, waste products are liberated, and acting 

 as poisons produce the usual fever and chills. At the 

 time when the young parasites escape into the blood 

 they may be killed by giving properly graduated and 

 timed doses of quinine. 



Malarial Parasites in the Mosquito. — There are 



