350 RESEARCH IN PROTOZOOLOGY 



PASSERES have been found with infections than those of any other 

 order, and members of the family fringillid^ appear to be par- 

 ticularly susceptible. The parasites now being used in the labora- 

 tories in the United States were obtained from English sparrows 

 by Whitmore in New York in August, 191 3, by Hartman in Balti- 

 more in October, 1924, and by Hufif in Hampton, Virginia, in 

 September, 1926. Problems and methods of research with these 

 organisms are discussed in Chapters XXXVII to XXXIX inclu- 

 sive. 



Cold-blooded animals are also infected with malarial parasites, 

 particularly lizards. They have been reported from lizards of the 

 southern Sudan and Brazil. 



So far as we know the malarial parasites of both man and 

 lower animals are transmitted from one vertebrate host to another 

 by mosquitoes. A considerable body of information exists regard- 

 ing the mosquito vectors of human malaria and a little is known 

 regarding the transmitting agents of bird malaria (Huff, 1927) but 

 our information concerning the transmission of the other species is 

 very meager. 



PROBLEMS IN HUMAN MALARIA 



As noted above there are still many problems in human malaria 

 awaiting solution and many of the results already obtained need 

 confirmation. The following list presents in abbreviated form 

 some of these problems. Inasmuch as the life-cycle of the bird 

 malarial parasites and the effects of these parasites on their avian 

 hosts are remarkably similar to those of the human species many 

 of the problems suggested can be attacked with the aid of bird 

 malaria. This is now being done in the writer's laboratory where 

 work has been in progress for ten years and in other laboratories 

 both in this country and abroad. 



a. Life-cycle of malaria parasites in the vertebrate host. 



( I ) Where are the parasites located in the body at various stages 

 in the course of the infection and in what stages in their life- 

 cycles? The distribution of the stages is known to differ in P. 

 falciparum from that of the other two species. Why do specimens 

 of P. falciparum clog up the capillaries (Bass, 1920) ? Why does 

 schizogony of P. falciparum take place in the internal organs 

 instead of in the peripheral blood as in the other two species? 



