1 62 THE PROTOZOA 



trating new blood-corpuscles and there repeating the cycle ; and 

 under certain conditions they all produce flagellated bodies or spores 

 {Polymitus form, R\ They differ in the number of spores that are 

 formed, although in the same variety the number appears to be incon- 

 stant, so that mere difference in number cannot be considered a good 

 specific character. A much more satisfactory means of distinguishing 

 them lies in the regular periodicity of spore-formation, which accom- 

 panies well-marked morbid symptoms in the patient. Thus, in 

 Plasmodium vivax, spore-formation occurs every forty-eight hours (ap- 

 proximately) ; in P. malaria, every seventy-two hours. The pyrexial 

 attacks in all cases consist of similar symptoms, a stage of fever 

 following one of chill and followed by a stage of perspiring. Spore- 

 formation is the signal for a chill in the patient. The pigment 

 granules (melanin) become aggregated in the centre of the cell, 

 while the protoplasm breaks up into spores about them. The 

 blood-corpuscle which contains the parasite then disintegrates, and 

 the spores and melanin are liberated. It is supposed that this dis- 

 ruption of the corpuscle, by liberating a toxin (melanin) created and 

 stored up by the parasite, is the direct cause of the attack. If this 

 hypothesis, which is certainly based upon considerable evidence, 

 should be verified by future investigation, the malaria-organism will 

 be the only protozoon known to produce poisonous growth-products. 

 Quinine in the system is apparently fatal to the parasite by preventing 

 its growth and sporulation. 



The spores of the malaria organism are not covered by a protective 

 coating as in the majority of Telosporidia, and are, therefore, unsuited 

 for an exposed life outside of their host. It was early recognized, 

 however, that there must be an extra-corporeal period in the life- 

 history of the parasite in order that the species should be perpetuated. 

 That there actually is such a period is shown by the spread of the 

 disease throughout a community. 1 Nevertheless, the whereabouts 

 of the organism and its form during the extra-corporeal existence 

 have remained a mystery until within the last few years. The key 

 to the puzzle has been given by the flagellated body or Polymitus 

 form. The blood when examined fresh from a malaria patient 

 shows the ordinary form of the parasite, but after a short period 

 of exposure to the air (10 to 30 minutes, Manson, '98), the 

 parasite develops long flagelliform processes, which vibrate with 

 great vigor and not infrequently break away from the body of 

 the cell to swim about like Spirilla in the plasm. Danilewsky 

 ('91) believed this stage to be an independent flagellated parasite 

 of a special nature, and he named it Polymitus. Lave>an, Metsch- 



1 In Italy it is estimated that 2,000,000 people are ill every year with malaria (Santori, 

 1900). 



