The Human Malarial Parasites 



533 



Plasmodium vivax. At the end of twenty-four hours the 

 organism seems to extend itself more or less linearly, and 

 sometimes appears as a long drawn band which crosses 

 the substance of the unchanged corpuscle. In another 

 twenty-four hours the breadth of the parasite is two or 

 three times as great, and it has become pigmented. The 

 corpuscle itself is still unchanged. In the last twenty- 

 four hours the parasite enlarges, becomes more or less 

 quadrilateral, finally rounds up, shows depressions upon 

 the surface corresponding to the divisions into which it . is 

 to segment, the pigment gathers at the center, and the 

 substance undergoes cleavage resulting in the formation of 

 from six to fourteen, but usually eight, spores. It is to be 



Fig. 173. Parasite of quartan malarial fever: a, b, c, d, Enlarging 

 intracellular parasites; e, }, g, h, segmentating parasites forming a dis- 

 tinct rosette from which the spores separate; i, macrogametocyte; ;, 

 microgametocyte; k, flagellum. 



noticed that it is not until a few hours before segmentation 

 that the parasite becomes as large as the corpuscle, and that 

 the corpuscle is never enlarged or bleached by the presence 

 of the parasite. The meroblasts form regular rosettes, or 

 "daisy-heads," within the corpuscles. 



In single infections the parasites are all of the same age 

 and all mature at the same time, so that in any examination 

 of the blood they will all appear uniform. It is, however, 

 sometimes true that the patient may have been infected one 

 day by one mosquito bite, and again infected the next day 

 or the third day by a second mosquito bite, so that his blood 

 contains two crops of the microparasites, arriving at maturity 

 at different times. This perplexes the clinician through the 

 variety of parasitic forms in the blood and the abnormal fre- 

 quency of the paroxysms. 



