170 OTHER SPOROZOA 



side the cells or blood corpuscles, at least during part of their 

 life history. On the other hand, in these diseases there have 

 been discovered bodies of various kinds within the cells, inter- 

 preted by some workers as true parasites, by others as reaction 

 products of the cells. These bodies have received zoological 

 names, e.g., the Negri bodies of hydrophobia were named Neuro- 

 hydrophobice, the cell inclusions in smallpox Cytoryctes 

 3, and so on. It is now a commoner belief that these bodies 

 coHist of material extruded from the nucleus of the cell into its 

 cytoplasm where it surrounds one or many of the minute or- 

 ganisms during the intracellular portion of their life history. 



For these problematical organisms, minute in size, of uncertain 

 life history, and apparently enshrouded in a mantle of extruded 

 nuclear material during their intracellular life, the name Chlamy- 

 dozoa (meaning mantle animals) has been given. Whether these 

 bodies have b^g^prrectly interpreted as described above' and 

 whether they snWna be considered Protozoa is open to question. 

 Their animal nature has not been sufficiently demonstrated to 

 warrant more than brief mention of them and the diseases they 

 cause in a treatise o^fcnimal parasites. 



In the following paragraphs the sporozoan parasites and ob- 

 scure or invisible parasites which have been briefly mentioned 

 above will be discussed in Wlttle more detail in the following 

 order: (1) coccidians, (2) Rhyiosporidium, (3) Sarcosporidia, 

 (4) Oroya fever, (5) the yellow fever group, (6) the spotted fever 

 group, (7) Chlamydozoa. 



Coccidians 



There are a number of serious diseases of animals which are 

 caused by parasites of the class Sporozoa known as coccidians. 

 These are very small animals, without distinct organs of lo- 

 comotion, which have both an asexual and a sexual phase in 

 their life history (Fig. 48). The asexual phase is not unlike 

 what takes place in the asexual phase of malaria parasites, ex- 

 cept that the parasites live inside of cells lining the intestine 

 instead of in the blood. Like the malaria parasites, a coccidian, 

 within the epithelial cell in which it is living (Fig. 48A-C), di- 

 vides into two, four, eight, sixteen, or perhaps twenty or more 

 daughter cells, arranged somewhat like the segments of an 

 orange (Fig. 48D). The young coccidians, escaping from the 



