ANIMAL PARASITES. 115 



small irregular colorless body within the red blood-cell. 

 This body increases gradually in size until it quite 

 fills the cell. As it grows, pigment-granules appear, 

 which at first are peripherally placed, but later collect 

 in a clump in the center of the parasite. At this stage 

 the parasite has matured, and its whole body splits 

 up into spores, or new young parasites which, upon 

 rupture of the red blood-corpuscle, are set free in the 

 blood and attach themselves to fresh cells. In an 

 infected person large numbers of plasmodia appear to 

 reach maturity and sporulate about the same time, and 

 it has been found that the chills and fever correspond 

 with this division of the parasites. 



In tertian malarial jever, the plasmodium attains 

 maturity in forty-eight hours, in quartan fever, seventy- 

 two hours, facts which seem to explain the regularity 

 of the chills in these two forms of ague. In cBstivo- 

 autumnal fever another special variety of parasite is 

 concerned which attains maturity in from twenty-four 

 to forty-eight hours, in consequence of which the course 

 of this form of ague is irregular. 



During the course of all the malarias there are also 

 formed in the blood oval, spherical, or crescentic 

 bodies, some of which are flagellated, others non-flagel- 

 lated. These are sexual elements of the parasites, the 

 flagellated forms constituting the males, the non-flagel- 

 lated, the females. Union of these in the blood, how- 

 ever, for some unknown reason, does not take place, 



