FORMS OF THE MALARIAL PARASITE 523 



of the red corpuscles, becoming intra-corpuscular amoebulse ; the 

 cycle is thus completed. The parasites are most numerous in 

 the blood during the development of the pyrexia, and, further, 

 they are also much more abundant in the internal organs than in 

 the peripheral blood ; in the malignant type, for example, the 

 process of sporulation is practically confined to the former. 



In addition to these forms which are part of the ordinary 

 asexual cycle, there are derived from the amoebulse other forms, 

 which are called gametocytes, or sexual cells. These remain 

 unaltered during successive attacks of pyrexia, and undergo no 

 further change until the blood is removed from the human body. 

 In the simple tertian and quartan fevers (vide infra] the gameto- 

 cytes resemble somewhat in appearance the fully developed 

 amcebulas before sporulation, whereas in the malignant type they 

 have a characteristic crescent-like or sausage-shaped form ; hence 

 they are often spoken of as " crescentic bodies." 



The various forms of the parasite seen in the human blood 

 may now be described more in detail. 



1. The Enhoemospores (Lankester) or Merozoites are the 

 youngest and smallest forms resulting from the segmentation of 

 the adult amoebula sporocyte or schizont. They are of round 

 or oval shape and of small size, usually not exceeding 2 //. in 

 diameter; the size, however, varies somewhat in the different 

 types of fever. A nucleus and peripheral protoplasm can be 

 distinguished (Fig. 159). The former appears as a small 

 rounded body which usually remains unstained, but contains a 

 minute mass of chromatin which stains a deep red with the 

 Romano wsky method ; the peripheral protoplasm is coloured 

 fairly deeply with methylene-blue. The spores show little or 

 no amoeboid movement ; at first free on the plasma, they soon 

 attack the red corpuscles, where they become the intra-corpuscular 

 amcebulre. If the blood, say in a mild tertian case, be examined 

 in the early stages of pyrexia, one often finds at the same time 

 sporulating forms, free spores, and the young amcebulas within 

 the red corpuscles. 



2. Intra-corpuscular Amoebulce or Trophozoites. These include 

 the parasites which have attacked the red corpuscles ; they are at 

 first situated on the surface of the latter but afterwards penetrate 

 their substance. They usually occur singly in the red corpuscles, 

 but sometimes two or more may be present together. The 

 youngest or smallest forms appear as minute colourless specks, 

 of about the same size as the spores. As seen in fresh blood, 

 they exhibit more or less active amoeboid movement, showing 

 marked variations in shape. The amount and character of the 



