62$ MALARIAL FEVER 



schizont vary in the different types. In the quartan there are 

 6-12, and the segmentation is in a radiate manner, giving rise 

 to the characteristic daisy-head appearance ; in the tertian they 

 number 15-20 or more, and have a somewhat rosette-like 

 arrangement (Fig. 178); in the malignant there are usually 

 6-20 merozoites of small size and somewhat irregularly arranged. 

 Gametocytes. As stated above, these are sexual cells which 

 are formed from certain of the amoebulse, and which undergo no 

 further development in the human subject. In the mild tertian 

 and quartan fevers they are rounded and resemble somewhat 

 the largest amoebulse. The female cells, macrogametocytes, are 

 of large size, measuring up to 1 6 /A in diameter ; they contain 

 coarse grains of pigment, and the protoplasm stains somewhat 

 deeply with methylene-blue. The male cells, microgametocytes, 

 are smaller, and the protoplasm stains faintly ; the nucleus, 

 generally in the centre, is rich in chromatin. In the malignant 

 fevers the gametocytes have the special crescentic or sausage- 

 shaped form mentioned above. They measure 8 to 9 JJL in length, 

 and occasionally a fine curved line is seen joining the extremities 

 on the concave aspect, which represents the envelope of the red 

 corpuscle (Fig. 181). They are colourless and transparent, and 

 are enclosed by a distinct membrane ; in the central part there 

 is a collection of pigment and granules of chromatin. The male 

 crescents can be distinguished from the female by their appear- 

 ance ; the former are somewhat sausage-shaped, the pigment is 

 less dark and more scattered through the cell, and there are 

 several granules of chromatin ; the latter have more pointed 

 ends and their substance stains more deeply with the blue, the 

 pigment is dark and concentrated, often in a small ring, and 

 there are one or two masses of chromatin in the centre of the 

 crescent (Plate V., Fig. 22 /, g). According to the Italian 

 observers, the early forms of the crescents are somewhat fusi- 

 form in shape and are produced in the bone-marrow. The fully 

 developed crescents do not appear in the blood till several days 

 after the onset of the fever, and they may be found a con- 

 siderable time after the disappearance of the pyrexial attacks. 

 They are also little, if at all, influenced by the administration 

 of quinine. Ross and Thomson have enumerated directly (p. 640) 

 the malarial parasites in the blood at different stages of the disease, 

 and have found that a certain relationship exists between the 

 asexual and the sexual forms, a rise in the number of the former 

 being followed eight to ten days later by a rise in the number of 

 the latter ; they accordingly consider that this is probably the 

 period necessary for the development of the sexual forms. They 



