592 MALARIAL FEVER 



which in their turn infect the red 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, 

 namely, (a) the full development of the sexual cells or gameto- 

 cytes, and (b) the impregnation of the female (Plate V., Fig. 

 21 tn-y). 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. 165-167). 

 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. 168). They are of considerable length but of great fine- 

 ness, and often show 7 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. In the female cell, which has also assumed 

 the rounded form, maturation takes place by the giving off of 

 part of the nuclear chromatin, this process corresponding to 

 the formation of a polar body. Impregnation occurs by the 

 entrance of a microgamete, the chromatin of the two cells after- 

 wards becoming fused. Impregnation was first observed by 

 McCallum in the case of halteridium, and, he found that the 

 female cell afterwards acquired the power of independent move- 

 ment 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 to 8 //. 

 in diameter, and containing clumps of pigment, may be found in 



