THE MALARIAL PARASITE 283 



required for the sexual cycle. The spores which are formed in schizogony are known 

 as merozoites. 



Merozoites may best be distinguished from sporozoites by the presence of a 

 nuclear karyosome, this being absent in sporozoites. In Eimeria we have the 

 oocyst containing four sporocysts with two sporozoites in each sporocyst while in 

 Isospora we have an oocyst containing two sporocysts with four sporozoites in each. 



Eimeria stiedae. This sporozoon is usually known as the Coccidium cuniculi 

 or C. omforme. It is most frequently found in the epithelium of the bile ducts. 

 It has very rarely been reported for man. In these cases (about five) cysts of the 

 liver have been found containing coccidia. The parasite is about 40 X 20/z, and is 

 oval in shape with a double outlined integument. The sporozoites, which form 

 inside, are falciform in shape. These escape and enter fresh epithelial cells, and 

 thus the process of schizogony goes on. The parasites of the liver are larger than 

 those found in the intestines, these latter being only about 30 X 15/1- In the fceces 

 the form most often found is the oocyst, about 40 X 2o/*. Infection takes place by 

 ingestion of the oocyst. 



Wenyon states that the Eimeria oocysts, found in cases from Gallipoli, are round 

 instead of the usual oval. They are about 20 microns in diameter and contain four 

 sporocysts, 10X7 microns, each of which has two sporozoites with one or two highly 

 refractile residual bodies. 



Isospora bigemina. This parasite, formerly called the Coccidium bigeminum, 

 lives in the intestinal villi of dogs and cats. It is about 12X8/4 and shows a highly 

 refractile envelope (oocyst) containing two biscuit-shaped sporocysts within each of 

 which are four sporozoites. It has been reported for man three times. 



Cases from the Gallipoli district also showed oocysts of Isospora with two sporocysts 

 and four sporozoites in each. 



Haemosporidia 



Of the Sporozoa found in the blood (Haemosporidia), the malarial 

 parasites are the only ones connected with disease in man. 



There are at least three species of animal parasites which produce human malaria, 

 Plasmodium vivax, the cause of benign tertian, P. malaria of quartan and P. falci- 

 parum of sestivo-autumnal. These parasites belong to the haemamceba type of the 

 order Heemosporidia, of the class Sporozoa and of the phylum Protozoa. 



This type of Haemosporidia is characterized by invasion of red 

 cells, amoeboid movement, pigment production and the extrusion of 

 flagellum-like processes from the male sporont after the blood is taken 

 from the animal and allowed to cool. 



Other Hajmospordia which are very important in diseases of domesticated animals, 

 but not for man, are those of the piroplasm type. 



These parasites of the red cells do not produce pigment and do not "exflagellate." 

 It is to parasites of this type that some authorities have ascribed the cause of black 

 water fever, a condition undoubtedly connected with malaria. 



