498 



PROTOZOA 



cysts pass with the food into the stomach, where the cyst wall and the 

 spore sack are destroyed and the sporozoites are set free. The motile 

 sporozoites pass through the ductus choledochus into the liver, some 

 probably passing into the intestines and infecting the cells directly, 

 a later infection of the intestines occurring from forms developed in the 

 liver. The organism develops within the epithelial cells of the liver and 

 gall-ducts until the cells are finally broken down and tissue cysts are 

 formed, within which, after more or less complicated changes, cysts of 

 the parasite are again formed. 



FIG. 152 



a b c d e f g h i 



Showing spore formation in coccidium cuniculi from the liver of the rabbit : a and b, young stage 

 in the epithelial cells of the gall-ducts (the small oval is the cell nucleus); c, d, and e, the fertilized 

 oocyst ; in d the protoplasm is beginning to shrink away from the cyst wall, and in e it has con- 

 tracted into a spherical form ; /, segmentation into four sporoblasts ; g, elongation of the sporoblasts 

 to form spores ; h, four complete spores in the oocyst ; i, single spore more highly magnified, show- 

 ing the two sporozoites and a small quantity of residual protoplasm. The life cycle has been fuUy 

 worked out by Simon. (After Balbiani, from Doflein.) 



A few cases of human infection of the liver with the coccidium cunic- 

 uli have been reported. The coccidium hominis Rivolta found a few 

 times in the human intestines, as well as similar coccidia found in the 

 intestines of lower animals, may belong to the same species. 



Coccidium bigeminum (Stiles) is found in the feces of dogs, cats, pole- 

 cats, and possibly human beings. The organism is characterized by 

 the division of the oocyst into two united cysts, containing four spores. 

 The size is 8ft to 15/>. The life cycle is not well known. 



Coccidioides Immitis Rixford and Gilchrist (1897). 



The organism occurring in certain cases of skin and lung infection in 

 man and described under the above name was classed by the authors with 

 the coccidia; but it has been shown by Moffitt, Ash, and especially by 

 Ophiils to be a mould, its fungous-like characters developing on the 

 usual artificial culture media. The description given by Rixford and 

 Gilchrist of the morphology of the parasite in the tissues is the same 

 as that of the organisms studied by Ophiils. In each nodule formed in 

 the disease one to several parasites are found either free or lodged 

 in a giant cell. The parasites have the form of "rounded protoplasmic 

 masses 20/J. to 80// in diameter, surrounded by a thick, enveloping 

 membrane. Their multiplication is effected by a series of bipartitions 

 which go on within the membrane ; the latter then bursts and sets free 

 the young parasitic elements, which grow in situ or are carried away 

 by the blood or lyinph." Among Ophiils' conclusions are the follow- 

 ing: " The lesions produced by this fungus fall under the general head 



