248 ANIMAL PARASITES 



PLASMODIUM FALCIPARUM 



The plasmodium of aestivo-autumnal fever, or pernicious ma- 

 larial fever, also called tropical. The outbreaks of this occur ir- 

 regularly. The disease produced by them is very much more 

 malignant and is harder to cure. The young spore appears in 

 the corpuscle as a small hyaline body, smaller than the other 

 forms and much more active. The size and shape of the red cells 

 are little if any altered but they become granular and polychro- 

 matophilic. The pigment is very finely granular and the body 

 frequently presents the signet-ring appearance. There may be 

 more than one parasite to a red cell. The cycle of development 

 (schizogony) is twenty-four to forty-eight hours. The plas- 

 modium in its schizogony divided into 8 to 24 merozoites or spores, 

 and are arranged in a spore-like form. The extracorpuscular bod- 

 ies may resemble a crescent or sickle; this form is very character- 

 tic of aestivo-autumnal fever. There are two forms of these 

 crescents, one delicate, the male, and one larger and ovoid, the 

 female. They are very resistant to quinine and persist for a long 

 period in the blood. Plasmodia undergoing schizogony are often 

 found in the brain capillaries after death, which accounts for the 

 cerebral symptoms in such cases. This form can be differentiated 

 from the others by the irregular and pernicious type of fever pro- 

 duced; by its great resistance to quinine; the fewer number of 

 merozoites; the finely granular appearance of the pigment; the 

 relatively small size of the young intracorpuscular body; and, 

 by the ring shape of some of the young forms. 



Often, in blood from malarial cases, pigmented leucocytes are 

 seen, and ghost, or shadow, red corpuscles from which the haemo- 

 globin has been dissolved are often met with. Spherical extra- 

 corpuscular bodies become flagellated (gametes) in freshly drawn 

 blood. The parasite may be studied in fresh film preparations 

 and by staining dried films by methylene blue and eosin, Roma- 

 nowsky's, or Jenner's methods. They are much more frequent 

 in the pyrexial period, and when quinine has not been given. 



