PROTOZOA AND DISEASE 



89 



The individual parasite lives in a red blood corpuscle, into which it enters 

 while in the spore stage. Then it changes to a form resembling a minute 

 ameba. It feeds upon the contents of the corpuscle and when full grown 

 nearly fills it. The parasite then sporulates. The rupture of the cyst 

 formed in sporulation, accompanied by the rupture of the wall of the 

 corpuscle, liberates numerous spores into the fluid of the blood. These 

 enter other corpuscles and pass through a similar fife history. The setting 

 free of spores from many infected corpuscles corresponding to the starting 



j^ 



,rit'^ rec^ b/ooafcoA-^ 



POs 





Asexual 

 cycle 

 in man 



/ \ \ GamefO' 



Asexual spore'l^ {m'j 7 



Enter mosQu/fo 



Sex-ucil cycle 



in mosquito 



Macro- {v^|8 

 gamete 



W^Tygote 



Ookinete 



13 Oocyst 



Fig. 36. — Diagram of the life cycles of the malarial parasite of the tertian type, show- 

 ing the asexual cycle in man and the sexual cycle in an anopheline mosquito. Stages 1 to 6 

 show the entrance of the spores into a red blood corpuscle and the growth and sporulation 

 of the parasite. Stage 7, the production of gametocytes. Stage 8, their transformation into 

 gametes. Stages 9 and 10, fertilization and the zygote. Stages 11 and 12, the change of the 

 zygote to an active form, the ookinete, which penetrates the wall of the stomach and encysts. 

 Stage 1.3, forming an oocyst below the outer layer of the stomach wall. Stages 14 and 15, 

 the development of several sporoblasts in the oocyst, the development from each of many 

 spores, and their dispersal into the body cavities. And stage 16, the entrance of these spores 

 into the salivary gland. They are introduced with the saliva into a human being, stage 17, 

 enter red blood corpuscles, and another cycle is begun. 



of a new generation, is accompanied by the liberation of poisons in the 

 blood which cause an attack of chills and fever. The time between these 

 attacks, therefore, indicates the period between generations of the 

 parasite. These intervals are 24, 48, or 72 hours, corresponding to three 



