532 Malaria 



vary glands, entering into the epithelial cells and taking 

 radial positions about the nuclei, where they remain for a 

 time. Later, they leave the cells with the saliva, and when 

 the mosquito again bites, enter the warm-blooded host to 

 infect it, if of the appropriate species. 



The whole cycle in the mosquito varies, according to the 

 external temperature, from ten days to a fortnight. The 

 mosquito may remain alive for more than one hundred days, 

 and must bite frequently to satisfy its needs. It remains 

 infective so long as the sporozoits remain in the saliva, which 

 is usually as long as the insect is alive. Here it may be 

 remarked that as it is only the female mosquitoes that bite, 

 it is only by them that the infection can be spread. It is 

 an interesting question, not yet solved, whether any of the 

 sporozoits entering into the mosquito's ovaries can infect 

 its eggs so that a new generation of mosquitoes may be born 

 infective. The longer the human infection persists, the 

 greater the number of gametocytes formed, until sometimes, 

 especially in aestivo-autumnal malaria, no schizonts are any 

 longer found, though the blood contains large numbers of 

 gametocytes. In such cases the gametocytes, especially the 

 crescents of sestivo-autumnal fever, but sometimes also those 

 of tertian and quartan fever undergo regressive schizogony in 

 the patient's blood, and without fertilization suddenly break 

 up into spores which enter the red blood-corpuscles and 

 occasion a relapse of the infection that had apparently spent 

 itself. 



THE HUMAN MALARIAL PARASITES. 



There are three known forms of human malarial parasites: 

 Plasmodium malariae, Plasmodium vivax, and Plasmodium 

 falciparum. 



I. Plasmodium Malariae (Laveran,* 1880). This is the 

 smallest of the human malarial parasites. Its occurrence is 

 relatively infrequent, as is that of the quartan fever that 

 it occasions. The schizogonic period is seventy-two hours 

 long, and as each is completed, a paroxysm of the disease 

 occurs. 



The parasite, in the red blood-corpuscle, first appears as 

 a tiny ring, at one side of which there is a chromatin dot. 

 At this time the organism cannot be differentiated from 



* "Acad. de Med.," Nov. 23, Dec. 28, 1880. 



