692 INFECTION AND IMMUNITY. 



ures from 70 to 100 microns in lengths and from 

 50 to 70 in breadth. Proliferation is through sim- 

 ple division. Conjugation has been noted. Invo- 

 lution cysts are Bypherical and surrounded by a 

 dense membrane. 

 pathogenic The parasite is found in the intestines of the hog 



Significance. ^ ^ Q ^ ag .^ man ^ &n( J fa Q f ormer ma y fa {fa nor _ 



mal host. It occurs also in sewage waters and has 

 been found in drinking water. Infections have 

 been noted in those having nothing to do with hogs. 

 The organisms may reach the intestines of man in 

 an encapsulated state (?). It is found in diar- 

 rheal conditions in man rarely, and the question 

 is still open as to whether the parasite is able to 

 cause enteritis independently or whether it merely 

 aggravates and prolongs an enteritis due to other 

 causes. 



The cecum and colon show the principal changes 

 at autopsy, and are of an inflammatory and ulcera- 

 tive nature. 



A smaller species, B. minutum, has also been 

 observed in the intestines of man. 



VII. CEKCOMONAS INTESTINALIS. 



Morphology. This organism is small and colorless, the form 

 spherical or oval. The single flagellum is for the 

 most part very large and is situated at the anterior 

 end (in the direction in which the parasite 

 moves) ; the posterior end is long drawn out and 

 is subject to changes in form. Sharp pseudopodia 

 are sometimes formed. The nucleus lies in the 

 anterior half of the body, and either here or on the 

 sides are one or more vacuoles. A mouth opening 

 is not differentiated, but at the base of the flagel- 

 lum food is taken in at a particular point through 



