294 BACTERIOLOGY FOR NURSES 



of Anopheles may be distinguished by their spotted wings. Another 

 distinction exists in that in the female Anopheles the palpi are as 

 long as the proboscis, whereas in the female Culex they are always 

 shorter. The eggs and larvae of the two genera also differ; the 

 eggs of Anopheles are single and are supported on the surface of 

 the water by air cells, those of Culex are numerous and attached 

 together in masses by a cementing substance. The breathing tube 

 of the Anopheline larvae is short and its angle with the body 

 necessitates that the larvse lie parallel with the surface of the 

 water, while that of Culex permits the body to lie at an angle with 

 the surface. 



Varieties of Malarial Parasites. Three distinct varieties of 

 the malarial parasite have been described : Plasmodium malaria 

 the cause of quartan fever ; Plasmodium vivax the cause of tertian 

 fever ; and Plasmodium falciparum the cause of estivo-autumnal 

 fever. Certain authorities are of the opinion that two varieties 

 may be concerned in the latter condition. Only one, however, is 

 definitely known. The tertian and quartan fevers are more preva- 

 lent in temperate countries and are rarely fatal ; the estivo-autum- 

 nal type, the malignant or pernicious fever of the tropics, is of a 

 much more serious nature (Fig. 46). 



P. Malarias. The asexual cycle of development is completed 

 in seventy-two hours, the typical chill and fever occurring every 

 third day, or according to the Roman method of reckoning, every 

 fourth day. Double or even triple infection may occur. In the 

 latter case infection on three successive days would result in the 

 liberation of a brood of merozoites and the consequent clinical 

 symptoms every day. The young P. malariae are less active than 

 P. vivax ; the pigment is of a darker color, more coarsely granular, 

 and is arranged around the periphery of the parasite, while that 

 in the tertian parasite is distributed throughout the protoplasm. 

 P. malarise arranges itself as a band across the infected corpuscle. 

 When mature the adult forms do not exceed the size of the red 

 blood corpuscles, and the segments, usually six to twelve in number, 

 are arranged symmetrically around the central pigment, giving the 

 parasite at this stage the so-called daisy appearance. 



