352 RESEARCH IN PROTOZOOLOGY 



c. Relapse in malaria. 



(i) Parthenogenesis. What is the status of this phenomenon 

 and its relation to relapse? (Samsonoff, 1925.) 



(2) Do old red cells become immune? Are young cells more 

 frequently parasitized ? Would relapse result from the rapid in- 

 crease of young cells? 



(3) Is relapse due to changes in the blood plasma which make it 

 easier for merozoites to parasitize cells, or to changes in the 

 phagocytic power of leucocytes? 



(4) What effect has the administration of quinine on relapse? 



(5) What factors are responsible for latency in malaria? 



(6) Does the sugar content of the blood have an influence on 

 relapse? (See Chapter XXXIX.) 



(7) Is there a resistant stage or unknown stage of the parasite 

 that brings on relapses ? 



d. Species. 



(i) Is there a tcnuc stage in the life-cycle of P. falciparum? 

 (Russell, 1928.) 



(2) Are the species in man and primates the same? (Hegner, 

 1928.) 



(3) How many human species are there? 



(4) Are there two species or subspecies of P. falciparum? 

 (Craig, 1921 ; Darling, 1921.) 



(5) If a mosquito is fed on a mixed infection will it transmit 

 a mixed infection? If so, does this prove the plurality of species? 



(6) Is virulence related to different races of parasites? 



e. Relation of malaria parasites to the resistance of tJie host and to 



blood reactions? 

 (i) Do malaria patients acquire immunity? 



(2) Can a complement-fixation test be devised in malaria with 

 antigens prepared from cultures or organs? A precipitin test? 

 (Taliaferro and Taliaferro, 1928.) 



(3) What is the relation between the number of parasites in 

 the blood and clinical symptoms? 



(4) What factors are responsible for clinical symptoms? 



(5) Does dengue give immunity? 



(6) What is responsible for the pathogenicity of P. falciparum? 



(7) How do provocatives bring about increases in the number 

 of parasites in the blood ? 



