PARASITES 445 



517. Malaria. This disease is caused, not by a bacterium, 

 but by a very small animal organism which, during an attack 

 of the disease, swarms in the blood and attacks the red cor- 

 puscles. The life history of the organism and its method of 

 being spread from one patient to another one are quite re- 

 markable. When the organism gets into the human system, 

 it enters a red blood corpuscle and there multiplies by a pecul- 

 iar method of division. Finally, the corpuscle breaks down 

 and sets the new organisms free in the blood plasma. These 

 soon attack other corpuscles and repeat the process of repro- 

 duction. The breaking down of the corpuscles and the setting 

 free of the young parasites which seems to occur at about the 

 same time throughout the body of the patient, brings on the 

 chill which is characteristic of the disease. This process is 

 repeated * through generation after generation of the organ- 

 ism and so the patient has a chill at regular intervals. 



When a mosquito of a certain kind known as ANOPHELES 

 bites a person suffering with malaria, it takes some of the ma- 

 larial parasites into its stomach along with the blood. Here 

 the organism takes a very different course of development. It 

 first buries itself in the walls of the mosquito's stomach and a 

 complicated method of reproduction takes place. Finally, 

 great numbers of the organism collect on the salivary glands 

 of the mosquito and may later be injected into the body of 

 another human subject who is bitten by the mosquito. From 

 eight to ten days are required for the organism to complete 

 its development in the body of the mosquito and the mos- 

 quito is incapable of infecting a person during that time. 

 The disease is normally spread from person to person in no 

 other way than through the agency of mosquitos. 



It has been found that quinine is a poison to the malarial 

 parasite and therefore a specific cure for the disease. The 

 quinine seems to be more deadly to the young parasites just 

 set free from the blood corpuscles and, therefore, the time to 

 administer the quinine is just after the chill. 



Knowing the life history of the organism as we do, and 



