504 Malaria 



up, the column being not more than 5 cm. in length. The tip of 

 the tube is sealed, the excess of glass cut off, and then the remainder, 

 containing the blood is placed in the centrifuge and whirled again. 

 A small grayish mass of leukocytes and parasites rises to the top. 

 The capillary tube is cut just above this layer, and the grayish mass 

 removed with a fine capillary pipet is spread upon a slide and stained. 

 The parasites are so concentrated as to be easily found. 



The Human Malarial Parasites 



There are three known forms of human malarial parasites: Plas- 

 modium malariae, Plasmodium vivax, and Plasmodium falciparum. 

 I. Plasmodium Malariae (Laveran,* 1880). — ^This is the smallest 



Synonyms. — Oscillaria malariae pro parte, Laveran, 1881. Plasmodium var- 

 quartana, Golgi, 1890. Hajmamceba malariae, Grassi et Feletti, 1892. 

 Haemamoeba laverani var. quartana, Labbfi, 1894. Plasmodium malariae quart, 

 anum, Labb^, 1899. Haemomenas malariae, Ross, 1900. Plasmodium golgii, 

 Sambon, 1902. Plasmodium quartanas. Billet, 1904; Celli, 1904. 



of the human malarial parasites. Its occurrence is relatively infre- 

 quent, as is that of the quartan fever that it occasions. Theschiz- 

 ogonic period is seventy- two hours Jong, and as each is completed, 

 a paroxysm of the disease occurs. 



The parasite, in the red blood-corpuscles, first appears as a tiny 

 ring, at one side of which there is a chromatin dot. At this time the 

 organism cannot be differentiated from 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 stiU 

 unchanged. In the last twenty-four hours the parasite enlarges, 

 becomes more or less quadrilateral, finally rounds up, shows depres- 

 sions 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 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 nor 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 



* "Acad, de Med.," Nov." 23, Dec. 28, 1880. 



