220 PATHOGENIC MICROORGANISMS. 



MALARIA. 



Flasmodium Malariae. 



History. In 1880 Laveran discovered in the blood of cases 

 of intermittent fever a microorganism which he believed to 

 be the cause of this disease. This microorganism belongs to 

 the animal kingdom of the family of the protozoa, and has 

 received a number of names. The one generally applied 

 to-day is that of Plasmodium malariae. 



Later investigations have shown that this protozoa has two 

 cycles of existence. One cycle is reproduced in man, and the 

 other cycle in the body of some insects of the mosquito tribe, 

 the Anopheles claviger or Anopheles maculapennis. 



In the red blood-corpuscles of man the parasites go 

 through an undetermined number of life-cycles, and then 

 pass into the middle intestine of certain species of mosquitoes, 

 in which they go through the various phases of a new life- 

 cycle, ending in the salivary glands, and from these when the 

 mosquito bites a human being, in order to obtain nourish- 

 ment, the parasite passes again into man. 



The phase of life which is completed in man is the cause of 

 malarial fever. In the younger stages the parasites in this 

 life-cycle appear as very small amoaboid bodies, which have 

 a more or less rapid motion, and which are found in the red 

 blood-corpuscles, nourishing themselves with the substance of 

 these corpuscles and converting their haemoglobin into a 

 black pigment known as melanin. They increase in size, 

 cease their motion, and by a process of fission multiply ; the 

 daughter cells resulting from this fission become free in the 

 plasma and invade other blood-corpuscles, in which they go 

 through the same life-cycle. 



The two principal symptoms of malaria, ansemia and inter- 

 mittent fever, are related to this life-cycle, the anaemia being 

 due to the destruction of a large number of the red blood- 

 corpuscles by the parasites, and the fever is manifested when 

 the parasite is undergoing multiplication. 



In their growth the parasites of malaria have been shown 



