xiii, b, 2 Haughwout: Infections with Coccidium 81 



herpetomoniasis and Leishmania infections is strongly sug- 

 gestive of the possibility of the origin of kala-azar in man 

 from the bites of insects harboring herpetomonads. It is finally 

 beginning to dawn upon us, after many bitter lessons, that in 

 the past we have paid entirely too little attention to the relations 

 between parasites supposed to be specific to lower animals and 

 conditions of disease occurring in man. 



In dealing with the problem of coccidiosis in man, we are 

 greatly handicapped by the vagueness and lack of information 

 contained in reports on these infections. We have, so far as I 

 know, no report of clinical or pathological findings in any of 

 these cases, save the case reported by Davaine, (2) which dates 

 back to 1858, which will lend us much help. Until recently 

 the descriptions of the organisms found have been so incomplete 

 as to leave us in doubt, in most cases, as to which genus was 

 involved or, in many other cases, if, indeed, the organism was 

 a protozoon at all. We have no literature on the intracellular 

 phases in the cycle of the human parasite. Some of these re- 

 ports are of interest to the pathologist, but they leave much 

 to be desired from the viewpoint of the protozoologist. 



Coccidia are typically parasites of epithelial cells during their 

 trophic phases, but Smith (17) has pointed out that they may 

 be found between epithelial cells or even occupying subepithelial 

 positions; however, such conditions are more or less aberrant. 

 Infection takes place through the ingestion of matter contamin- 

 ated with the spores of the parasites, and liberation of the sporo- 

 zoites from the sporocysts takes place under the influence of 

 the digestive juices of the small intestine. The sporozoites. 

 which are minute, sickle-shaped bodies, penetrate the cell mem- 

 brane of the epithelial cells and come to rest in the cytoplasm, on 

 which they proceed to feed. As it feeds, each parasite grows, 

 the host cell becomes enormously hypertrophied, compressing 

 the adjacent cells, and the host-cell nucleus is crowded down to 

 the basement membrane. Finally the trophozoite has reached 

 the limit of size, multiple division (schizogony) takes place, 

 the cell membrane ruptures, and a number of merozoites are 

 set free to infect other epithelial cells. This is the so-called 

 asexual or multiplicative phase in the life cycle, and it is re- 

 peated for a variable number of generations until conditions 

 supervene that initiate the sexual or propagative phase, which 

 is spoken of as sporogony. 



Sporogony involves the production of sexually differentiated 

 gametes, their union in fertilization, and the subsequent forma- 



