MALARIA 73 



Wlien once injected into human blood the parasite again has the 

 risk of being killed, or it may lie dormant in the spleen to develop 

 when the resistance of the victim is reduced, or it may multiply and 

 cause an attack almost at once. 



Some da^■s must pass between the bite of an infected moscjuito and 

 the subseciuenl attack of fever, because the parasites must multiply 

 enormously and generate sufficient toxin to produce the fever. It has 

 been estimated that 350 millions of parasites are required in the body 

 to produce a rise in temperature of one degree F., hence one may find 

 parasites in the blood when an attack is not anticipated by the patient. 

 If but few parasites are injected by the mosquito the incubation period 

 is lengthened; if many parasites, then it is shortened. The average 

 time between the bite and the fever is nine to twelve da\'S. 



During tliis period there are premonitory symptoms, such as 

 lassitude, body pains, &c., so that quinine taken at this time may abort 

 the attack. 



The parasites may increase at a very rapid rate, as shown by Ross, 

 thus : Suppose that 1,000 protospores of P. vivax have entered the red 

 cells, only ten out of the fifteen to twenty spores produce, then they 

 will increase as follows : — 



Days ... 2 ... 4 ... 6 ... 10 fever ... 12 



Parasites... 10,000 ... 100,000 ... 1,000,000 ... 100,000,000 ... 1,000,000,000 



The rise of temperature is caused by the liberating of toxins when 

 the red cell is ruptured by the sporozoites. The sexual forms take 

 no part in producing the fever in the patient in whom they have been 

 found. 



The pigmentation of the cells and organs is due to the hjemozoin 

 liberated from the parasite as the cell ruptures. 



The liberated young spores attack and enter new red cells until the 

 majority of the red cells may be infected and a critical condition arise 

 for the patient. In some cases, e.g., C][uartan, the attacks may subside 

 owing probably to a partial immunity. 



The merozoites can pass through the placenta, infect the foetus and 

 cause congenital malaria, from which some racial immunity may be 

 established. 



The P. malaricB lives in the circulatory blood chiefly, and sporulates 

 there every seventy-two hours. It gives rise to general symptoms, 

 M'hich are known by the term quartan malarial fever. 



The P. vivax lives in the circulatory blood, but sporulates every 

 forty-eight hours chiefly in the spleen, causing general symptoms 

 known as tertian malarial fever. 



L. inalaricB causes a stickiness of the red cells so as to cause them 

 to adhere somewhat to the capillarv walls of the organs in which they 



