NUMBERS OF PARASITES 153 



body and deposited in the spleen or other organs or under the 

 skin, causing the sallow color so characteristic of malarial patients. 

 It is at the time of the bursting of the corpuscles and release of 

 the waste matters which act as poisons that the characteristic 

 chills and fever of malaria are felt. Since the cycle from one 

 generation to the next is usually about 48 hours in the sestivo- 

 autumnal parasite the attacks of ague are felt at these intervals. 

 In the malignant type of malaria the bursting of all the para- 

 sitized corpuscles and release of poisonous waste matter does not 

 occur so nearly simultaneously as it does in the other species, 

 the result being that the paroxysms of chill and fever are drawn 

 out over many hours. 



A " quotidian " type of malignant malarial fever in which 

 agues occur every 24 hours is occasionally met with, the parasites 

 of which are thought by some authors to constitute one, or even 

 two, distinct species. The majority of cases of malaria with 

 daily-recurring fevers are due to double or triple infections, the 

 different broods maturing on different days. 



This rapid process of multiplication in the human blood re- 

 sults in a short time in an enormous number of parasites, some- 

 times many billions. The actual quantity of parasites in a 

 human body in a case of severe sestivo-autumnal malaria has 

 been estimated at 600 cc., or over one pint. It may or may not 

 mean more to the reader to know that such a quantity of ma- 

 larial parasites would number 3,000,000,000,000. A better con- 

 ception of the real meaning of such a number may perhaps be 

 gained when it is realized that to count off this number at the 

 rate of 100. per minute day and night without cessation would 

 require 30 times the period of time that has elapsed since the 

 birth of Christ. Eventually, however, either the parasite kills 

 its host, which very commonly happens with this particular 

 species, or the host, by the development of a temporary immunity 

 in his body, kills or, as it more often happens, suppresses the 

 parasite. Such a course of events unaltered, would lead to a 

 very early and complete extermination of the parasite. There is 

 a second chapter in the life history of Plasmodium which saves 

 it from such an early death. 



After the parasites have been developing in the blood for about 

 two weeks or more there are developed special sexual forms or 

 gametocytes, male and female, in the form of sausage-shaped 



