CILOPHORA 437 



tidium infection from monkey to swine and back to monkey. 

 Still there is perhaps some question as to the identity of the para- 

 sites found in man and in hogs. 



Balantidium Minutum. Schaudinn in 1899 observed this 

 organism in the human feces. It is smaller than Bal. coli, the 

 greatest measurements being 20X30^, and the oral groove ex- 



FIG. 213. Spharophrya pusilla within a paramaecium. At one place there are 

 four parasites"and a fifth is escaping. Higher up, one of the parasites is just pene- 

 trating the host, and a single parasite is seen near the center of the paramaecium. 

 (From Doflein after Butschli.} 



tends more than half way back along the side of the cell. It 

 probably occurs rarely in the human small intestine. Other 

 species of balantidium have been described. 



Sphaerophrya Pusilla. This organism is of peculiar interest 

 because it lives as a parasite within another protozoon, the para- 

 mecium. The cell of Sph. pusilla is spherical, 20 to 40/4 in diam- 

 eter, and provided with sucking tentacles and cilia when outside 

 the body of the host. 



