MALARIA 15 



d. Merozoite: minute amoeboid spores that are liberated 

 from the red blood cells containing segmented schizonts, 

 and attack new red cells. 



e. Gametocyte: a stage that may develop from a tropho- 

 zoite. It does not segment but remains in the blood of 

 man until it degenerates or is sucked up by a mosquito. In 

 the stomach of the mosquito certain gametocytes change into 

 macrogametes; others produce filamentous microgametes. 



/. Fertilization: a stage that occurs in the stomach of the 

 mosquito during which a microgarnete fuses with a macro- 

 gamete. The resultant cell becomes a motile, vermiform 

 stage known as an ookinete. The ookinete penetrates the 

 wall of the stomach, becomes an oocyst and causes the 

 formation of a swelling projecting into the body cavity. 



g. Oocyst: a spherical body that develops from the 

 ookinete. It produces within it hundreds of sporozoites 

 which break out into the body cavity. Many of these 

 reach the salivary glands of the mosquito where they remain 

 until transferred to another animal when the mosquito bites. 



The periods occupied by the various stages are as follows : 

 (a) Growth from sporozoite or merozoite to full grown 

 schizont 30 hours; (b) segmentation 18 hours; (c) devel- 

 opment in mosquito from gametocytes to oocysts 40 hours; 

 (d) from oocysts to sporozoites 4 or 5 days. The asexual 

 cycle of Plasmodium vivax in man is 48 hours. The mos- 

 quitoes become infective about 8 days after they suck up 

 gametocytes. The principal differences between Plasmo- 

 dium vivax and P. malariae and P. falciparum are indicated 

 in the accompanying table (3) . 



4. Methods of making, films for the diagnosis of malaria. 

 1. Thin films, a. Equipment: Clean glass slides; small bot- 

 tle of alcohol; small package absorbent cotton; Hagedorn 

 needle fastened in cork of small vial and extending down 

 into alcohol. 



