506 PROTOZOA 



amount of such blood that anopheles mosquitoes may imbibe can ever 

 infect the mosquito. 



When studying old cases and relapses it will be seen that the char- 

 acteristics of the three varieties are lost to a certain extent. But other 

 factors will have changed accordingly; the paroxysms will have become 

 irregular, protracted, less severe, and will eventually occur widely apart. 

 Now, as the paroxysm depends upon the segmentation of the protozoon 

 or the probable liberation of a toxin, any changes in the morphology 

 might be expected to influence the periodicity and character of the 

 paroxysm, and such is actually seen to be the case. 



An abnormal temperature chart can usually be explained by proper 

 study of the forms of parasites present. If quinine has been admin- 

 istered it is to be considered, as its effect on the morphology of the 

 parasite is profound and rapid. The part most and first affected is the 

 blue staining body; later follow eccentricities of the chromatin, such 

 as multiple bodies in young forms, extension of chromatin bodies, and 

 dwarfing, just such changes as might have occurred in time if the body 

 had been allowed to combat the parasite without the aid of drugs. 



The notion that the parasites can be found only at the time of the 

 paroxysm is still in the minds of many; it is erroneous. 



The .ffistivo-autumnal Parasite. 



In a recent primary infection only young forms can be found in the 

 peripheral blood; their pigment is so scanty as to render their recog- 

 nition in fresh blood a matter of experience; dancing pigment is prac- 

 tically never seen in such cases. 



Later in the disease the gametocytes develop; they are absolutely 

 characteristic, readily found, and of diagnostic value. 



In the fresh blood the young parasite is seen as a fairly sharply de- 

 fined, rounded, slightly amoeboid body; the infected corpuscle may be 

 crenated; it may have what has been termed a "brassy" appearance. 



Such forms stained show extremely thin and small rings, with one 

 or more chromatin bodies, situated not infrequently within the achro- 

 matic zone. There are frequently several parasites in one corpuscle; 

 five, six, and seven have been seen. Later the parasite shows a few 

 heavy, blackish, pigment granules, and an increase in the size of the body 

 is seen. It is very exceptionally that one finds in the peripheral blood 

 forms approaching segmentation or actually segmenting. The various 

 steps of chromatin division seem to take place chiefly in the bone- 

 marrow and the viscera. The parasite does not ordinarily attain the 

 size of the tertian form, and there are usually fewer segments. Their 

 arrangement is apt to be very symmetrical. 



Upon developing the gametocytes these are seen at times in large 

 numbers. They are first ovoidal and later crescentic. The blackish 

 pigment lies in a wreath around the thus hidden chromatin filaments. 

 There may be a corpuscular remnant or not. There seems to be a sort 



