THE SPOROZOA 209 



the nucleus, accompanied by absorption of its contents. The linin 

 framework is broken up, vacuoles are formed in it, and the 

 chromatin fuses into irregular lumps and strands. The nucleus 

 becomes enlarged to six or even ten times its normal diameter by 

 absorption of fluid from the cell. The chromatic substance is 

 forced out, by growth of the parasite, to the periphery of the 

 nucleus, and ultimately disappears, so that "the entire nucleus is 

 transformed into a gigantic vacuole, in the interior of which the 

 parasite floats" (Schaudinn). The cytoplasm of the cell, on the 

 other hand, is absorbed and shrivels up rapidly as the nucleus 

 enlarges, without going through any stage of hypertrophy such as 

 results from extranuclear parasitism. 



Each individual trophozoite in this way brings about the destruc- 

 tion of a cell, but of one only, in its host. Nevertheless, the parasites 

 are often present in such vast numbers that the epithelium of the 

 organ affected may be completely destroyed, and the host itself 

 killed or reduced to the last extremity. In centipedes experi- 

 mented upon by Schaudinn, the faeces became milk-white during 

 the acute stage of the Coccidiosis, and consisted entirely of epithelial 

 remains and Coccidian cysts. The intestine may be so stripped of 

 its epithelium that the young sporozoites are unable to find an 

 epithelial cell to infect, in which case they may attack a full- 

 grown Coccidian of another species, but never of their own kind 

 (Schaudinn [51]). In the mole, Cydospora caryolytica is the cause of 

 a pernicious form of enteritis accompanied by violent diarrhoea, 

 which is generally fatal to the host (Schaudinn [5 la]). In 

 rabbits young animals are often killed by the attacks of Coccidia 

 infesting the epithelium of the bile -ducts, and similar cases are 

 known in the human species. 1 The liver is greatly enlarged, and 

 its blood-vessels compressed, leading to functional derangements ; 

 the secretion of bile is reduced to a minimum ; the blood becomes 

 pale and watery, as in pernicious anaemia ; the respiration becomes 

 gasping, and the animal finally dies in convulsions. In all these 

 cases the destructive power of the parasite varies directly as its 

 power of multiplying by schizogony, and so overrunning the tissues 

 which it attacks ; and it is a very interesting and important fact, 

 that in no case, apparently, can the schizogony continue indefinitely, 

 but has its own natural, intrinsic limit, after which conjugation, 

 with consequent sporogony, is necessary for the recuperation of the 

 parasite and the continuance of its race. If, therefore, the patient 

 can safely pass the acute stage, the disease heals itself through the 

 failing reproductive powers of the parasite, on the one hand, and 

 the regenerative capacity of the epithelium on the other. The 

 injury inflicted on the host is repaired more or less completely; 



1 For a full account of the pathology of Coccidiosis, with special reference to man, 

 see Blanchard [30]. 



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