PROTOZOA AND DISEASE 91 



and therefore cannot become infected and transmit the disease. The 

 sexes may be distinguished by their antennae; those of the male are 

 complexly branched and have a feathery appearance, while those of the 

 female are simple, straight, and hairlike. 



The malarial parasite belongs to the genus Plasmodium. Three 

 species are recognized, corresponding to the three forms of the disease. 

 Plasmodiuvi vivax (Grassi and Feletti), producing tertian malaria, 

 is the common one in the United States. 



The malarial-fever parasite was discovered in Algeria in 1880 by a 

 French army doctor, Laveran, who found it in the blood of patients suffer- 

 ing from malaria. In 1883 a Dr. King of Washington, D. C, presented 

 evidence to show the transmission of the parasite by the mosquito; and 

 this transmission was demonstrated experimentally by Sir Ronald Ross, 

 an Englishman, in 1898. An Itahan, Grassi, and his pupils worked out 

 the complete life cycle. Previous to these discoveries it was generally 

 believed that the disease could be acquired by the breathing of miasma 

 rising from swamps and marshes, and the name, meaning literally bad air, 

 was given because of this superstition. Owing to the work of the investi- 

 gators named and others, it is now a fact of common knowledge that 

 malaria can be conveyed to a person only through the bite of an infected 

 mosquito of the proper kind. 



