570 



PATHOGENIC SPOROZOA 



may invade new epithelial cells of the same host, and may again 

 subdivide in an asexual manner. After this has occurred a number 

 of times the female merozoites begin to grow and to accumulate 

 nutritive material in their protoplasm. They then fall out of the cell 

 which they have infected and destroyed, and they reduce the amount 

 of their nuclear chromatin by the formation of polar bodies and the 

 expulsion of some chromatin. These are the phenomena of maturation 

 through which a germ cell must always pass before it can be fertilized 

 by another germ cell, which likewise has had to go through the same 

 process of maturation. While the female merozoites have in this 

 manner become the macrogametes, the male merozoites have gone 

 through a series of nuclear divisions and have formed a number of 

 spindle-shaped flagellated microgametes . The latter penetrate into the 

 macrogametes, and this, of course, constitutes the act of fertilization. 

 The copula formed by the union of the microgametes and macrogam- 

 etes later divides into two sporoblasts, or mother cells, giving rise 

 to the sporozoites, which are the result of the sexual fertilization and 

 propagation which have occurred. The oocyst containing the spores 

 may again be taken up by a new host, and the cycle can begin anew. 



FIG. 199 

 a b c d e f a h i 



Showing spore formation in Coccidium cuniculi, from the liver of a rabbit: a and 6, 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 contracted into a spherical form; f, 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, showing the two sporozoites and a small quantity of residual protoplasm. 

 The life cycle has been fully worked out by Simon. (After Balbiani, from Doflein.) 



Coccidium Cuniculi. The best and probably earliest known coccid- 

 ium pathogenic to mammals is the Coccidium cuniculi, or oviforme, 

 first described as Psorospermium cuniculi by Rivolta (1878). It 

 is parasitic in the intestinal epithelium and the liver cells of wild 

 and tame rabbits, and it sometimes causes fatal epidemics among 

 rabbits of laboratories and places where they are bred. The spore 

 cysts are taken up with food soiled by feces from animals harboring 

 the infection. After the cyst membrane has become dissolved the 

 sickle-shaped spores penetrate into the interior of the intestinal 

 epithelial cells of the host. The asexual forms are 20 to 50 micra 

 long and 20 to 35 micra wide; 30 to 200 merozoites are formed in 

 asexual reproduction. The coccidia disease of rabbits lasts from 

 one to two weeks, and leads to fever, diarrhea, and emaciation, with 



