76 DISEASES DUE TO PROTOZOA 



sanguinis, the pigment being liberated at the same time is then taken 

 up bv phagocytes, Avhich may also destroy many spherules. The 

 spherules which have escaped the phagocytes attack and enter new red 

 cells. The young parasite now shows active amoeboid movements, 

 shoots out long, retracting, slender pseudopodia, growing as it feeds 

 upon the haemoglobin, converting the latter into parasites, protoplasm 

 and iKemozoin particles. The movements gradually cease and 

 spherules are formed, completing the cycle. The ha?mozoin particles 

 show a Brownian movement, otherwise the particles are now passive. 



The voung parasite contains nucleus and nucleolus, which break 

 down and become diffused in the protoplasm, only to reappear as small 

 scattered nucleoli around which the parasite segments itself. As long 

 as the nucleus remains entire the h^emozoin is situated at the periphery ; 

 when the nucleus becomes segmented the h^emozoin becomes central. 



These facts are not sufficient to describe the latency of the parasites 

 in the body, and their recurrence causing later a typical attack of the 

 fever. It is known that good powers of resistance and quinine favour 

 latencv, but that reduced resistance discourages it. 



EXTRACORPOREAL OR MOSQUITO CYCLE. 



When fresh mounted malarial blood is watched under a microscope, 

 for ten to thirty minutes certain parasites may be seen to throw out 

 long slender processes, one to six, giving the cell a cuttle-fish-like 

 appearance. These flagella, or more correctly microgametes, act like 

 spermatozoa, since this is the male form. These vigorous filaments, 

 four to six times as long as the diameter of the body of the cell, break 

 away, swim free in the liquor sanguinis, and are lost to sight. 



These flagellated cells are derived from crescent bodies and other 

 large parasites just prior to the concentration of h^emazoin and seg- 

 mentation. Such bodies are only formed seven to ten days after the 

 onset of acute malarial symptoms. These cells may not be numerous, 

 but thev persist after all other forms of the parasite have disappeared, 

 and mav be seen from one to six weeks after all clinical symptoms have 

 cleared up. After this time they may gradually disappear. These 

 crescents are not affected by quinine. 



Thompson has shown that gametes as individuals do not persist, 

 but that there is an asexual cycle which produces the gametes from 

 time to time. The individual gametes do not live very long in the 

 peripheral circulation, probably about ten da}s ; if they persist after 

 that time it is because the asexual cycle has not been killed. Hence, 

 when gametes can be found relapse is always possible and probable. 

 Others agree with Thompson in this. 



The severity of the infection does not account for the relapses; the 

 mildest quartan will relapse time after time (James). 



