684 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



merozoite when the parasite divides; Plasmodium vivax forms about eighteen divisions, 

 Plasmodium malaria forms about eight. The adult sexual forms of Plasmodium 

 falciparum are shaped like a crescent. The three malarial parasites of man may be 

 distinguished from one another by these peculiarities as well as by other, lesser diff- 

 erences in themselves and in the red cells they parasitize. 



When a mature, asexual, malarial parasite bursts, it sets free young 

 parasites and a toxin. Practically all of the parasites, present in a person 

 suffering from acute malaria, mature and burst at the same time; the 

 considerable amount of toxin, set free in this way, produces the ague fit. 

 The young parasites of Plasmodium vivax mature in forty-eight hours; 



FIG. 127. Longitudinal section of Anopheles. A, head; B, thorax; C, abdomen; 

 i, oesophagus; 2, salivary glands; 3, dorsal reservoir; 4, ventral reservoir; 5, canal 

 entering stomach; 6, stomach; 7, malpighian tubes; 8, hind-gut; 9, rectum; 10, wings; 

 n, legs. (After Grassi from Lang and Dqflein.) 



consequently, a person infected by it has an ague fit when schizogony 

 occurs, on every third day, and the disease caused by it is called a tertian 

 fever. Plasmodium malaria matures in seventy-two hours ; consequently, it 

 causes an attack of ague on every fourth day andthe fever caused by it is 

 called quartan fever. Patients infected by Plasmodium falciparum have a 

 quotidian fever or aestivo-autumnal fever with a daily rise in the temper- 

 ature. There are three stages in an ague fit: during the cold stage, the 

 patient feels cold; in the hot stage he feels warm his temperature is 

 above normal during both stages; in the sweating stage the temperature 

 falls to normal and the patient's discomfort becomes much less. 



The regularly recurring ague fit is the only symptom characteristic of 

 malaria and a regular rise in temperature on the third or fourth days of an 

 illness is practically diagnostic of a malarial infection. The type of dis- 



