528 MALARIAL FEVER 



corpuscles and start the cycle again. As described and figured 

 by him, the chromatin of the macrogametocyte divides first into 

 two portions, one of which is smaller and stains more deeply 

 than the other. This more deeply-staining portion then divides, 

 and the protoplasm becomes segmented as in ordinary schizogony, 

 and a young brood of parasites results. The more faintly-staining 

 chromatin along with part of the protoplasm breaks up and 

 disappears. 



The Cycle in the Mosquito. As already explained, this 

 starts from the gametocytes. After the blood is shed, or after 

 it is swallowed by the mosquito, two important phenomena 

 occur, viz. (a) the full development of the sexual cells or 

 gametocytes, and (6) the impregnation of the female. If the 

 blood from a case of malignant infection be examined in a moist 

 chamber, preferably on a warm stage, under the microscope, 

 both male and female gametocytes may be seen to become oval 

 and afterwards rounded in shape (Figs. 162-164). Thereafter, 

 in the case of the male cell, a vibratile or dancing movement of 

 the pigment granules can be seen in the interior, and soon 

 several flagella-like structures shoot out from the periphery 

 (Fig. 165). They are of considerable length but of great fineness, 

 and often show a somewhat bulbous extremity. By the 

 Romanowsky method they have been found to contain a delicate 

 core of chromatin, which is covered by protoplasm. They 

 represent the male cells proper, that is, they are sperm -cells or 

 spermatozoa ; they are also known as microgametes. They 

 become detached from the sphere and move away in the 

 surrounding fluid. The female cell also assumes the rounded 

 form, and maturation takes place by the giving off of part of 

 the nuclear chromatin. Impregnation occurs by the entrance of 

 a microgamete, the chromatin of the two cells afterwards 

 becoming fused. Impregnation was first observed by MacCallum 

 in the case of halteridium, and he found that the female cell 

 afterwards acquired the power of independent movement or 

 became a "travelling vermicule." He also observed the 

 impregnation of the malignant parasite. The fertilised female 

 cell is now generally spoken of as a zygote or ookinete. 



It has been established that the phenomena just described 

 occur within the stomach of the mosquito, and that the fertilised 

 cell or zygote penetrates the stomach wall and settles between 

 the muscle fibres ; on the second day after the mosquito has 

 ingested the infected blood small rounded cells about 6-8 //, in 

 diameter and containing clumps of pigment may be found in 

 this position. (It was in fact the character of the pigment 



