HOST-PARASITE RELATIONS! INTESTINAL PROTOZOA 



that he has "observed several cases in which typical 

 amoebic ulcerations containing the amoebae were present 

 in the lower portion of the ileum in the region just above 

 the ileocaecal valve." Sellards and Theiler (1924) work- 

 ing with cats found that in several of the older animals 

 with histolytica infections of several weeks the amoebae 

 spread into the small intestine above the ileo-colic sphinc- 

 ter. They found that by ligating the large intestine and 

 then forcing water into the digestive tract with a stomach 

 tube they were able to cause the distension of the ileo- 

 colic sphincter. In 3 kittens thus treated the amoebae in- 

 fected the lower part of the small intestine, this result 

 suggesting that the sphincter ordinarily mechanically 

 prevents the passage of the amoebae into the ileum. In 3 

 other kittens no infection was obtained when the ileum 

 was ligated and trophozoites injected above the ligature. 

 Why the wall of the ileum is not as readily attacked as 

 that of the large intestine is not known. 



The distribution of amoebcp to other parts of the body. 

 A number of other secondary sites of infection with E. 

 histolytica have been noted besides the ileum; many of 

 these have been in parts of the body at a considerable 

 distance from the large intestine and can be explained 

 only on the assumption that amoebae are carried there in 

 the blood or lymph. When an amoebic ulcer is formed in 

 the wall of the large intestine blood vessels are opened, 

 thus giving the amoebae access to the blood stream ; speci- 

 mens have actually been observed in the capillaries of 

 the intestinal wall. Such amoebae may obviously be car- 

 ried to any part of the body and may initiate infections 

 wherever suitable conditions are encountered. 



94 



