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University of California Publications in Zoology ["Vol. 13 



stain and with hematoxylin and eosin, as well as in fresh smears 

 stained in the same manner, there are small acid staining granules 

 within the epithelial cells which suggest a stage of fragmentation. 

 However, we are not able, at this time, to so relate the changes 

 in the cell inclusions that any conclusive resemblance to a com- 

 plete protozoan life cycle is produced. 



IMMUNITY 



All who have worked with the disease have noted the develop- 

 ment of a complete immunity. Lowenthal (1906) says this im- 

 munity is shortlived, lasting only one to two months, while others, 

 as Reischauer (1906), say it lasts during the lifetime of the 

 fowl. Still others, as Schmid (1909), say it varies with the 

 severity of the original infection. We are not pi-epared at pres- 

 ent to agree or disagree with any of these observations, as the 

 greatest time between original inoculation and an attempted re- 

 inoculation which has elapsed in our series is thirty-five days. 

 Complete immiuiity was present at the end of that time. 



Early Immunity Incomplete. — Reischauer (1906) observes 

 that within the first week following the original inoculation there 

 is no immunity, but that later than this a reinfection runs a very 

 light course or is negative. Marx and Sticker (1902) found the 

 immunitj^ complete after twelve days. 



Our results, which confirm these latter observations, are given 

 in the following table : 



